Grade 9 Mathematics Learners Module Answer Key

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1. DRAFT March 24, 2014 i Mathematics Learner's Material Unit 1 Department of Education Republic of the Philippines 9 This instructional material was collaboratively developed and reviewed by educators from public and private schools, colleges, and/or universities. We encourage teachers and other education stakeholders to email their feedback, comments, and recommendations to the Department of Education at action@deped.gov.ph. We value your feedback and recommendations.
2. DRAFT March 24, 2014 ii Mathematics – Grade 9 Learner's Material First Edition, 2014 Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalties. Borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this book are owned by their respective copyright holders. Every effort has been exerted to locate and seek permission to use these materials from their respective copyright owners. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education Secretary: Br. Armin A. Luistro FSC Undersecretary: Dina S. Ocampo, Ph.D. Department of Education-Instructional Materials Council Secretariat (DepEd-IMCS) Office Address: 5th Floor Mabini Building, DepEd Complex Meralco Avenue, Pasig City Philippines 1600 Telefax: (02) 634-1054 or 634-1072 E-mail Address: imcsetd@yahoo.com
3. DRAFT March 24, 2014 iii TABLE OF CONTENTS QUARTER 1 Module No. 1: Quadratic Equations and Inequalities Lesson 1 Illustrations of Quadratic Equations 11 Lesson 2A Solving Quadratic Equations by Extracting Square Roots 19 Lesson 2B Solving Quadratic Equations by Factoring 30 Lesson 2C Solving Quadratic Equations by Completing The Square 39 Lesson 2D Solving Quadratic Equations By Using The Quadratic Formula 53 Lesson 3 The Nature of the Roots of a Quadratic Equation 65 Lesson 4 The Sum and the Product of Roots of Quadratic Equations 77 Lesson 5 Equations Transformable to Quadratic Equations 90 Lesson 6 Solving Problems Involving Quadratic Equations 104 Lesson 7 Quadratic Inequalities 114 Module 2. Quadratic Functions Lesson 1 Introduction to Quadratic Function 146 Lesson 2 Graphs of Quadratic Functions 164 Lesson 3 Finding the Equation of a Quadratic Function 181 Lesson 4 Applications of Quadratic Functions 200
4. DRAFT March 24, 2014 1 LEARNING MODULE MATH 9 MODULE NO. 1: QUADRATIC EQUATIONS AND INEQUALITIES INTRODUCTION AND FOCUS QUESTIONS: Was there any point in your life when you asked yourself about the different real life quantities such as costs of goods or services, incomes, profits, yields and losses, amount of particular things, speed, area, and many others? Have you ever realized that these quantities can be mathematically represented to come up with practical decisions? Find out the answers to these questions and determine the vast applications of quadratic equations and quadratic inequalities through this module. LESSONS AND COVERAGE: In this module, you will examine the above questions when you take the following lessons: Lesson 1 – ILLUSTRATIONS OF QUADRATIC EQUATIONS Lesson 2 – SOLVING QUADRATIC EQUATIONS  EXTRACTING SQUARE ROOTS  FACTORING  COMPLETING THE SQUARE  QUADRATIC FORMULA SALES PROFITS
5. DRAFT March 24, 2014 2 Lesson 3 – NATURE OF ROOTS OF QUADRATIC EQUATIONS Lesson 4 – SUM AND PRODUCT OF ROOTS OF QUADRATIC EQUATIONS Lesson 5 – EQUATIONS TRANSFORMABLE TO QUADRATIC EQUATIONS (INCLUDING RATIONAL ALGEBRAIC EQUATIONS) Lesson 6 – APPLICATIONS OF QUADRATIC EQUATIONS AND RATIONAL ALGEBRAIC EQUATIONS Lesson 7 – QUADRATIC INEQUALITIES In these lessons, you will learn to: Lesson 1  illustrate quadratic equations; Lesson 2  solve quadratic equations by: (a) extracting square roots; (b) factoring; (c) completing the square; (d) using the quadratic formula; Lesson 3  characterize the roots of a quadratic equation using the discriminant; Lesson 4  describe the relationship between the coefficients and the roots of a quadratic equation; Lesson 5  solve equations transformable to quadratic equations (including rational algebraic equations); Lesson 6  solve problems involving quadratic equations and rational algebraic equations; Lesson 7  illustrate quadratic inequalities;  solve quadratic inequalities; and  solve problems involving quadratic inequalities.
6. DRAFT March 24, 2014 3 MODULE MAP: Here is a simple map of the lessons that will be covered in this module: Quadratic Equations, Quadratic Inequalities, and Rational Algebraic Equations Illustrations of Quadratic Equations Solving Quadratic Equations Extracting Square Roots Factoring Completing the Square Quadratic Formula Nature of Roots of Quadratic Equations Sum and Product of Roots of Quadratic Equations Equations Transformable to Quadratic Equations Applications of Quadratic Equations and Rational Algebraic Equations Illustrations of Quadratic Inequalities Solving Quadratic Inequalities Applications of Quadratic Inequalities Rational Algebraic Equations Quadratic Inequalities
7. DRAFT March 24, 2014 4 PRE-ASSESSMENT Part I Directions: Find out how much you already know about this module. Choose the letter that you think best answers the question. Please answer all items. Take note of the items that you were not able to answer correctly and find the right answer as you go through this module. 1. It is a polynomial equation of degree two that can be written in the form ax2 + bx + c = 0, where a, b, and c are real numbers and a ≠ 0. A. Linear Equation C. Quadratic Equation B. Linear Inequality D. Quadratic Inequality 2. Which of the following is a quadratic equation? A. 142 2  rr C. 01452  ss B. 1273 t D. 372 2  xx 3. In the quadratic equation 0473 2  xx , which is the quadratic term? A. 2 x B. x7 C. 2 3x D. 4 4. Which of the following rational algebraic equations is transformable to a quadratic equation? A. 7 4 2 2 1     ww C. 4 3 2 1 3 12 qq   B. 5 1 32    pp D. mmm 7 2 4 2 3     5. How many real roots does the quadratic equation 0752  xx have? A. 0 B. 1 C. 2 D. 3 6. The roots of a quadratic equation are -5 and 3. Which of the following quadratic equations has these roots? A. 01582  xx C. 01522  xx B. 01582  xx D. 01522  xx 7. Which of the following mathematical statements is a quadratic inequality? A. 0532 2  rr C. 0273 2  tt B. 0127 h D. 01582  ss
8. DRAFT March 24, 2014 5 8. Which of the following shows the graph of 672  xxy ? A. C. B. D. 9. Which of the following values of x make the equation 01872  xx true? I. -9 II. 2 III. 9 A. I and II B. II and III C. I and III D. I, II, and III 10. Which of the following quadratic equations has no real roots? A. 342 2  xx C. 523 2  ss B. 0482  tt D. 072 2  rr 11.What is the nature of the roots of the quadratic equation if the value of its discriminant is zero? A. The roots are not real. C. The roots are rational and not equal. B. The roots are irrational and not equal. D. The roots are rational and equal. y x y x y x y x
9. DRAFT March 24, 2014 6 12.One of the roots of 020132 2  xx is 4. What is the other root? A. 5 2  B. 2 5  C. 5 2 D. 2 5 13.What are the roots of the quadratic equation 0562  xx ? A. 2 and -1 B. 8 and -7 C. -8 and 7 D. 3 and -2 14.What is the sum of the roots of the quadratic equation 01462 2  xx ? A. -7 B. -3 C. 6 D. 14 15.Which of the following quadratic equations can be solved easily by extracting square roots? A. 01272  xx C. 094 2 t B. 0372 2  ww D. 0823 2  vv 16.Which of the following coordinates of points belong to the solution set of the inequality 152 2  xxy ? A. (-3,2) B. (-2,9) C. (1,6) D. (3,1) 17.A 3 cm by 3 cm square piece of cardboard was cut from a bigger square cardboard. The area of the remaining cardboard was 40 cm2. If s represents the length of the bigger cardboard, which of the following expressions give the area of the remaining piece? A. 9s B. 92 s C. 92 s D. 402 s 18.The length of a wall is 12 m more than its width. If the area of the wall is less than 50 m2, which of the following could be its length? A. 3 m B. 4 m C. 15 m D. 16 m 19.The length of a garden is 5 m longer than its width and the area is 14 m2. How long is the garden? A. 9 m B. 7 m C. 5 m D. 2 m 20.A car travels 20 kph faster than a truck. The car covers 480 km in two hours less than the time it takes the truck to travel the same distance. How fast does the car travel? A. 44 kph B. 60 kph C. 80 kph D. 140 kph 21.A 12 cm by 16 cm picture is mounted with border of uniform width on a rectangular frame. If the total area of the border is 288 cm2, what is the length of the side of the frame? A. 8 cm B. 16 cm C. 20 cm D. 24 cm
10. DRAFT March 24, 2014 7 22.SamSon Electronics Company would like to come up with an LED TV such that its screen is 560 square inches larger than the present ones. Suppose the length of the screen of the larger TV is 6 inches longer than its width and the area of the smaller TV is 520 square inches. What is the length of the screen of the larger LED TV? A. 26 in. B. 30 in C. 33 in. D. 36 in. 23. A. I and II B. I and III C. II and III D. I, II, and III 24.It takes Mary 3 hours more to do a job than it takes Jane. If they work together, they can finish the same job in 2 hours. How long would it take Mary to finish the job alone? A. 3 hours B. 5 hours C. 6 hours D. 8 hours 25.An open box is to be formed out of a rectangular piece of cardboard whose length is 12 cm longer than its width. To form the box, a square of side 5 cm will be removed from each corner of the cardboard. Then the edges of the remaining cardboard will be turned up. If the box is to hold at most 1900 cm3, what mathematical statement would represent the given situation? A. 360122  xx C. 40082  xx B. 380122  xx D. 40082  xx 26.The length of a garden is 2 m more than twice its width and its area is 24 m2. Which of the following equations represents the given situation? A. 122  xx C. 242  xx B. 1222  xx D. 2422  xx The figure on the right shows the graph of 142 2  xxy . Which of the following is true about the solution set of the inequality? I. The coordinates of all points on the shaded region belong to the solution set of the inequality. II. The coordinates of all points along the parabola as shown by the broken line belong to the solution set of the inequality. III. The coordinates of all points along the parabola as shown by the broken line do not belong to the solution set of the inequality. y x
11. DRAFT March 24, 2014 8 27.From 2004 through 2012, the average weekly income of an employee in a certain company is estimated by the quadratic expression 224044.516.0 2  nn , where n is the number of years after 2004. In what year was the average weekly income of an employee equal to Php2,271.20? A. 2007 B. 2008 C. 2009 D. 2010 28.In the figure below, the area of the shaded region is 144 cm2. What is the length of the longer side of the figure? A. 8 cm B. 12 cm C. 14 cm D. 18 cm 6 cm 4 cm s s
12. DRAFT March 24, 2014 9 Part II Directions: Read and understand the situation below then answer or perform what are asked. Mrs. Villareal was asked by her principal to transfer her Grade 9 class to a new classroom that was recently built. The room however still does not have fixtures such as teacher's table, bulletin boards, divan, bookshelves, and cabinets. To help her acquire these fixtures, she informed the parents of her students about these classroom needs. The parents decided to donate construction materials such as wood, plywood, nails, paints, and many others. After all the materials have been received, she asked her students to make the designs of the different classroom needs. Each group of students was assigned to do the design of a particular fixture. The designs that the students will prepare shall be used by the carpenter in constructing the tables, chairs, bulletin boards, divan, bookshelves, and cabinets. 1. Suppose you are one of the students of Mrs. Villareal. How will you prepare the design of one of the fixtures? 2. Make a design of the fixture assigned to your group. 3. Illustrate every part or portion of the fixture including their measurements. 4. Using the design of the fixture made, determine all the mathematics concepts or principles involved. 5. Formulate problems involving these mathematics concepts or principles. 6. Write the expressions, equations, or inequalities that describe the situations or problems. 7. Solve the equations, the inequalities, and the problems formulated. Rubric for Design 4 3 2 1 The design is accurately made, presentable, and appropriate. The design is accurately made and appropriate. The design is not accurately made but appropriate. The design is made but not appropriate.
13. DRAFT March 24, 2014 10 Rubric for Equations Formulated and Solved 4 3 2 1 Equations and inequalities are properly formulated and solved correctly. Equations and inequalities are properly formulated but not all are solved correctly. Equations and inequalities are properly formulated but are not solved correctly. Equations and inequalities are properly formulated but are not solved. Rubric on Problems Formulated and Solved Score Descriptors 6 Poses a more complex problem with 2 or more correct possible solutions and communicates ideas unmistakably, shows in-depth comprehension of the pertinent concepts and/or processes and provides explanations wherever appropriate. 5 Poses a more complex problem and finishes all significant parts of the solution and communicates ideas unmistakably, shows in- depth comprehension of the pertinent concepts and/or processes. 4 Poses a complex problem and finishes all significant parts of the solution and communicates ideas unmistakably, shows in-depth comprehension of the pertinent concepts and/or processes. 3 Poses a complex problem and finishes most significant parts of the solution and communicates ideas unmistakably, shows comprehension of major concepts although neglects or misinterprets less significant ideas or details. 2 Poses a problem and finishes some significant parts of the solution and communicates ideas unmistakably but shows gaps on theoretical comprehension. 1 Poses a problem but demonstrates minor comprehension, not being able to develop an approach. Source: D.O. #73 s. 2012
14. DRAFT March 24, 2014 11 LEARNING GOALS AND TARGETS: After going through this module, you should be able to demonstrate understanding of key concepts of quadratic equations, quadratic inequalities, and rational algebraic equations, formulate real-life problems involving these concepts, and solve these using a variety of strategies. Furthermore, you should be able to investigate mathematical relationships in various situations involving quadratic equations and quadratic inequalities. LESSON NO. 1: ILLUSTRATIONS OF QUADRATIC EQUATIONS What to KNOW: Activity 1: Do You Remember These Products? Directions: Find each indicated product then answer the questions that follow. 1.  73 2 x 6.   44  xx 2.  42 ss 7.   5252  rr 3.   37  ww 8.  2 43 m 4.   29  xx 9.   7272  hh 5.   512  tt 10.   xx 3838  Questions: a. How did you find each product? b. In finding each product, what mathematics concepts or principles did you apply? Explain how you applied these mathematics concepts or principles. c. How would you describe the products obtained? Start Lesson 1 of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in understanding quadratic equations. As you go through this lesson, think of this important question: "How are quadratic equations used in solving real-life problems and in making decisions?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your work with your teacher.
15. DRAFT March 24, 2014 12 Are the products polynomials? If YES, what common characteristics do these polynomials have? Activity 2: Another Kind of Equation! Directions: Below are different equations. Use these equations to answer the questions that follow. 1. Which of the given equations are linear? 2. How do you describe linear equations? 3. Which of the given equations are not linear? Why? How are these equations different from those which are linear? What common characteristics do these equations have? Activity 3: A Real Step to Quadratic Equations Directions: Use the situation below to answer the questions that follow. Mrs. Jacinto asked a carpenter to construct a rectangular bulletin board for her classroom. She told the carpenter that the board's area must be 18 square feet. 1. Draw a diagram to illustrate the bulletin board. 2. What are the possible dimensions of the bulletin board? Give at least 2 pairs of possible dimensions. 3. How did you determine the possible dimensions of the bulletin board? Were you able to find and describe the products of some polynomials? Were you able to recall and apply the different mathematics concepts or principles in finding each product? Why do you think there is a need to perform such mathematical tasks? You will find this out as you go through this lesson. 0352  xx 732  ts 0259 2 r 83 2 1 2  xx 512  nc 106  qp 1549  x 06 4 3 h 1238 k 0144 2  mm 0672  tt 1442 r In the activity you have just done, were you able to identify equations which are linear and which are not? Were you able to describe those equations which are not linear? These equations have common characteristics and you will learn more of these in the succeeding activities.
16. DRAFT March 24, 2014 13 4. Suppose the length of the board is 7 ft. longer than its width. What equation would represent the given situation? 5. How would you describe the equation formulated? 6. Do you think you can use the equation formulated to find the length and the width of the bulletin board? Justify your answer. In the equation, ax2 is the quadratic term, bx is the linear term, and c is the constant term. Example 1: 2x2 + 5x – 3 = 0 is a quadratic equation in standard form with a = 2, b = 5, and c = -3. Example 2: 3x(x – 2) = 10 is a quadratic equation. However, it is not written in standard form. To write the equation in standard form, expand the product and make one side of the equation zero as shown below.   1023 xx  1063 2  xx 10101063 2  xx 01063 2  xx The equation becomes 3x2 – 6x – 10 = 0, which is in standard form. In the equation 3x2 – 6x – 10 = 0, a = 3, b = -6, and c = -10. How did you find the preceding activities? Are you ready to learn about quadratic equations? I'm sure you are!!! From the activities done, you were able to describe equations other than linear equations, and these are quadratic equations. You were able to find out how a particular quadratic equation is illustrated in real life. But how are quadratic equations used in solving real-life problems and in making decisions? You will find these out in the activities in the next section. Before doing these activities, read and understand first some important notes on quadratic equations and the examples presented. A quadratic equation in one variable is a mathematical sentence of degree 2 that can be written in the following standard form. ax2 + bx + c = 0, where a, b, and c are real numbers and a ≠ 0 Why do you think a must not be equal to zero in the equation ax2 + bx + c = 0?
17. DRAFT March 24, 2014 14 Example 3: The equation (2x + 5)(x – 1) = -6 is also a quadratic equation but is not written in standard form. Just like in Example 2, the equation (2x + 5)(x – 1) = -6 can be written in standard form by expanding the product and making one side of the equation zero as shown below.    6152  xx  65522 2  xxx 6532 2  xx 666532 2  xx 0132 2  xx The equation becomes 2x2 + 3x + 1 = 0, which is in standard form. In the equation 2x2 + 3x + 1 = 0, a = 2, b = 3, and c = 1. When b = 0 in the equation ax2 + bx + c = 0, it results to a quadratic equation of the form ax2 + c = 0. Examples: Equations such as x2 + 5 = 0, -2x2 + 7 = 0, and 16x2 – 9 = 0 are quadratic equations of the form ax2 + c = 0. In each equation, the value of b = 0. What to PROCESS: Your goal in this section is to apply the key concepts of quadratic equations. Use the mathematical ideas and the examples presented in the preceding section to answer the activities provided. Learn more about Quadratic Equations through the WEB. You may open the following links. http://library.thinkquest.org/20991/alg2/quad .html http://math.tutorvista.com/algebra/quadratic- equation.html http://www.algebra.com/algebra/homework/ quadratic/lessons/quadform/
18. DRAFT March 24, 2014 15 Activity 4: Quadratic or Not Quadratic? Directions: Identify which of the following equations are quadratic and which are not. If the equation is not quadratic, explain. 1. 1583 m 6. rr 425 2  2. 01052  xx 7.   723 xx 3. 0412  x 8.   06 2 1 h 4. 1272 2  tt 9.   02 2 x 5. 0326 2  xx 10.    1458  ww Activity 5: Does It Illustrate Me? Directions: Tell whether or not each of the following situations illustrates quadratic equations. Justify your answer by representing each situation by a mathematical sentence. 1. The length of a swimming pool is 8 m longer than its width and the area is 105 m2. 2. Edna paid at least Php1,200 for a pair of pants and a blouse. The cost of the pair of pants is Php600 more than the cost of the blouse. 3. A motorcycle driver travels 15 kph faster than a bicycle rider. The motorcycle driver covers 60 km in two hours less than the time it takes the bicycle rider to travel the same distance. 4. A realty developer sells residential lots for Php4,000 per square meter plus a processing fee of Php25,000. One of the lots the realty developer is selling costs Php625,000. 5. A garden 7 m by 12 m will be expanded by planting a border of flowers. The border will be of the same width around the entire garden and has an area of 92 m2. Were you able to identify which equations are quadratic? Some of the equations given are not quadratic equations. Were you able to explain why? I'm sure you did. In the next activity, you will identify the situations that illustrate quadratic equations and represent these by mathematical statements. Did you find the activity challenging? Were you able to represent each situation by a mathematical statement? For sure you were able to identify the situations that can be represented by quadratic equations. In the next activity, you will write quadratic equations in standard form.
19. DRAFT March 24, 2014 16 Activity 6: Set Me To Your Standard! Directions: Write each quadratic equation in standard form, ax2 + bx + c = 0 then identify the values of a, b, and c. Answer the questions that follow. 1. 723 2  xx 6.    xxx 377  2. xx 625 2  7.   084 2 x 3.    043  xx 8.    232 2  xx 4.    0172  xx 9.    22 112  xx 5.   1532 xx 10.     3342  xxxx Questions: a. How did you write each quadratic equation in standard form? b. What mathematics concepts or principles did you apply to write each quadratic equation in standard form? Discuss how you applied these mathematics concepts or principles. c. Which quadratic equations did you find difficult to write in standard form? Why? d. Compare your work with those of your classmates. Did you arrive at the same answers? If NOT, explain. How was the activity you have just done? Was it easy for you to write quadratic equations in standard form? It was easy for sure! In this section, the discussion was about quadratic equations, their forms and how they are illustrated in real life. Go back to the previous section and compare your initial ideas with the discussion. How much of your initial ideas are found in the discussion? Which ideas are different and need revision? Now that you know the important ideas about this topic, let's go deeper by moving on to the next section.
20. DRAFT March 24, 2014 17 What to REFLECT ON and FURTHER UNDERSTAND: Activity 7: Dig Deeper! Directions: Answer the following questions. 1. How are quadratic equations different from linear equations? 2. How do you write quadratic equations in standard form? Give at least 3 examples. 3. The following are the values of a, b, and c that Edna and Luisa got when they expressed 2 235 xx  in standard form. Edna: a = 2; b = 3; c = -5 Luisa: a = -2; b = -3; c = 5 Who do you think got the correct values of a, b, and c? Justify your answer. 4. Do you agree that the equation 2 234 xx  can be written in standard form in two different ways? Justify your answer. 5. a. How are you going to represent the number of Mathematics Club members? b. What expression represents the amount each member will share? c. If there were 25 members more in the club, what expression would represent the amount each would share? d. What mathematical sentence would represent the given situation? Write this in standard form then describe. Your goal in this section is to take a closer look at some aspects of the topic. You are going to think deeper and test further your understanding of quadratic equations. After doing the following activities, you should be able to answer this important question: How are quadratic equations used in solving real-life problems and in making decisions? The members of the school's Mathematics Club shared equal amounts for a new Digital Light Processing (DLP) projector amounting to Php25,000. If there had been 25 members more in the club, each would have contributed Php50 less.
21. DRAFT March 24, 2014 18 What to TRANSFER: Activity 8: Where in the Real World? 1. Give 5 examples of quadratic equations written in standard form. Identify the values of a, b, and c in each equation. 2. Name some objects or cite situations in real life where quadratic equations are illustrated. Formulate quadratic equations out of these objects or situations then describe each. Summary/Synthesis/Generalization: This lesson was about quadratic equations and how they are illustrated in real life. The lesson provided you with opportunities to describe quadratic equations using practical situations and their mathematical representations. Moreover, you were given the chance to formulate quadratic equations as illustrated in some real-life situations. Your understanding of this lesson and other previously learned mathematics concepts and principles will facilitate your learning of the next lesson, Solving Quadratic Equations. Your goal in this section is to apply your learning to real-life situations. You will be given a practical task which will demonstrate your understanding of quadratic equations. In this section, the discussion was about your understanding of quadratic equations and how they are illustrated in real life. What new realizations do you have about quadratic equations? How would you connect this to real life? How would you use this in making decisions? In this section, your task was to give examples of quadratic equations written in standard form and name some objects or cite real-life situations where quadratic equations are illustrated. How did you find the performance task? How did the task help you realize the importance of the topic in real life? Now that you have a deeper understanding of the topic, you are ready to do the tasks in the next section.
22. DRAFT March 24, 2014 19 LEARNING MODULE MATH 9 LESSON NO. 2A: SOLVING QUADRATIC EQUATIONS BY EXTRACTING SQUARE ROOTS What to KNOW: Activity 1: Find My Roots!!! Directions: Find the following square roots. Answer the questions that follow. 1. 16 = 6. 289 = 2. 25 = 7. 16.0 = 3. 49 = 8. 36 = 4. 64 = 9. 25 16 = 5. 121= 10. 256 169  = Questions: a. How did you find each square root? b. How many square roots does a number have? Explain your answer. c. Does a negative number have a square root? Why? d. Describe the following numbers: 8 , 40 , 60 , and 90 Start Lesson 2A of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in solving quadratic equations by extracting square roots. As you go through this lesson, think of this important question: "How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your answers with your teacher.
23. DRAFT March 24, 2014 20 Are the numbers rational or irrational? Explain your answer. How do you describe rational numbers? How about numbers that are irrational? Activity 2: What Would Make A Statement True? Directions: Solve each of the following equations in as many ways as you can. Answer the questions that follow. 1. 127 x 6. 355  x 2. 104 t 7. 1623 h 3. 35 r 8. 287  x 4. 210 x 9.   2473 x 5. 162 s 10.   28132 k Questions: a. How did you solve each equation? b. What mathematics concepts or principles did you apply to come up with the solution of each equation? Explain how you applied these. c. Compare the solutions you got with those of your classmates. Did you arrive at the same answers? If not, why? d. Which equations did you find difficult to solve? Why? Were you able to find the square roots of some numbers? Did the activity provide you with an opportunity to strengthen your understanding of rational and irrational numbers? In the next activity, you will be solving linear equations. Just like finding square roots of numbers, solving linear equations is also a skill which you need to develop further in order for you understand the new lesson. How did you find the activity? Were you able to recall and apply the different mathematics concepts or principles in solving linear equations? I'm sure you were. In the next activity, you will be representing a situation using a mathematical sentence. Such mathematical sentence will be used to satisfy the conditions of the given situation.
24. DRAFT March 24, 2014 21 Activity 3: Air Out!!! Directions: Use the situation below to answer the questions that follow. 1. Draw a diagram to illustrate the given situation. 2. How are you going to represent the length of a side of the square-shaped wall? How about its area? 3. Suppose the area of the remaining part of the wall after the carpenter has made the square opening is 6 m2. What equation would describe the area of the remaining part of the wall? 4. How will you find the length of a side of the wall? Activity 4: Learn to Solve Quadratic Equations!!! Directions: Use the quadratic equations below to answer the questions that follow. 1. Describe and compare the given equations. What statements can you make? 2. Solve each equation in as many ways as you can. Determine the values of each variable to make each equation true. x2 = 36 t2 – 64 = 0 2s2 – 98 = 0 Mr. Cayetano plans to install a new exhaust fan on his room's square-shaped wall. He asked a carpenter to make a square opening on the wall where the exhaust fan will be installed. The square opening must have an area of 0.25 m2. The activity you have just done shows how a real-life situation can be represented by a mathematical sentence. Were you able to represent the given situation by an equation? Do you now have an idea on how to use the equation in finding the length of a side of the wall? To further give you ideas in solving the equation or other similar equations, perform the next activity.
25. DRAFT March 24, 2014 22 3. How did you know that the values of the variable really satisfy the equation? 4. Aside from the procedures that you followed in solving each equation, do you think there are other ways of solving it? Describe these ways if there are any. Activity 5: Anything Real or Nothing Real? Directions: Find the solutions of each of the following quadratic equations, then answer the questions that follow. 1. How did you determine the solutions of each equation? 2. How many solutions does each equation have? Explain your answer. 3. What can you say about each quadratic equation based on the solutions obtained? Quadratic equations that can be written in the form x2 = k can be solved by applying the following properties: How did you find the preceding activities? Are you ready to learn about solving quadratic equations by extracting square roots? I'm sure you are!!! From the activities done, you were able to find the square roots of numbers, solve linear equations, represent a real-life situation by a mathematical sentence, and use different ways of solving a quadratic equation. But how does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? You will find these out in the activities in the next section. Before doing these activities, read and understand first some important notes on solving quadratic equations by extracting square roots and the examples presented. Were you able to determine the values of the variable that make each equation true? Were you able to find other ways of solving each equation? Let us extend your understanding of quadratic equations and learn more about their solutions by performing the next activity. x2 = 9 r2 = 0 w2 = -9 1. If k > 0, then kx 2 has two real solutions or roots: kx  . 2. If k = 0, then kx 2 has one real solution or root: 0x . 3. If k < 0, then kx 2 has no real solutions or roots.
26. DRAFT March 24, 2014 23 The method of solving the quadratic equation kx 2 is called extracting square roots. Example 1: Find the solutions of the equation x2 – 16 = 0 by extracting square roots. Write the equation in the form kx 2 . x2 – 16 = 0  x2 – 16 + 16 = 0 + 16 x2 = 16 Since 16 is greater than 0, then the first property above can be applied to find the values of x that will make the equation x2 – 16 = 0 true. x2 = 16  16x x = ±4 To check, substitute these values in the original equation. Both values of x satisfy the given equation. So the equation x2 – 16 = 0 is true when x = 4 or when x = -4. Answer: The equation x2 – 16 = 0 has two solutions: x = 4 or x = -4. Example 2: Solve the equation t2 = 0. Since t2 equals 0, then the equation has only one solution. That is, t = 0. To check: 02 t 00 ? 2  00  Answer: The equation t2 = 0 has one solution: t = 0. For x = 4: 0162 x 0164 ? 2  01616 ?  00  For x = -4: 0162 x   0164 ? 2  01616 ?  00 
27. DRAFT March 24, 2014 24 Example 3: Find the roots of the equation 092 s . Write the equation in the form kx 2 . 092 s  90992 s 92 s Since -9 is less than 0, then the equation 92 s has no real solutions or roots. There is no real number when squared gives - 9. Answer: The equation 092 s has no real solutions or roots. Example 4: Find the solutions of the equation (x – 4)2 – 25 = 0. To solve (x – 4)2 – 25 = 0, add 25 on both sides of the equation. (x – 4)2 – 25 + 25 = 0 + 25 The resulting equation is (x – 4)2 = 25. Solve the resulting equation. (x – 4)2 = 25  254 x x – 4 = ±5 Solve for x in the equation x – 4 = ±5. x – 4 + 4 = ±5 + 4  x = ±5 + 4 The equation will result to two values of x. Check the obtained values of x against the original equation. Both values of x satisfy the given equation. So the equation (x – 4)2 – 25 = 0 is true when x = 9 or when x = -1. Answer: The equation (x – 4)2 – 25 = 0 has two solutions: x = 9 or x = -1 x = 5 + 4 x = 9 x = -5 + 4 x = -1 For x = 9:   0254 2 x   02549 ? 2  0255 ? 2  02525 ?  00  For x = -1:   0254 2 x   02541 ? 2    0255 ? 2  02525 ?  00 
28. DRAFT March 24, 2014 25 What to PROCESS: Activity 6: Extract Me!!! Directions: Solve the following quadratic equations by extracting square roots. Answer the questions that follow. 1. x2 = 16 6. 4x2 – 225 = 0 2. t2 = 81 7. 3h2 – 147 = 0 3. r2 – 100 = 0 8. (x – 4)2 = 169 4. x2 – 144 = 0 9. (k + 7)2 = 289 5. 2s2 = 50 10. (2s – 1)2 = 225 Questions: a. How did you find the solutions of each equation? b. What mathematics concepts or principles did you apply in finding the solutions? Explain how you applied these. c. Compare your answers with those of your classmates. Did you arrive at the same solutions? If NOT, explain. Your goal in this section is to apply previously learned mathematics concepts and principles in solving quadratic equations by extracting square roots. Use the mathematical ideas and the examples presented in the preceding section to answer the activities provided. Learn more about Solving Quadratic Equations by Extracting Square Roots through the WEB. You may open the following links. http://2012books.lardbucket.org/books/begi nning-algebra/s12-01-extracting-square- roots.html http://www.purplemath.com/modules/solvqu ad2.htm http://www.personal.kent.edu/~bosikiew/Alg ebra-handouts/solving-sqroot.pdf
29. DRAFT March 24, 2014 26 Activity 7: What Does a Square Have? Directions: Write a quadratic equation that represents the area of each square. Then find the length of its side using the equation formulated. Answer the questions that follow. 1. 2. Questions: a. How did you come up with the equation that represents the area of each shaded region? b. How did you find the length of side of each square? c. Do all solutions to each equation represent the length of side of the square? Explain your answer. Was it easy for you to find the solutions of quadratic equations by extracting square roots? Did you apply the different mathematics concepts and principles in finding the solutions of each equation? I know you did! In this section, the discussion was about solving quadratic equations by extracting square roots. Go back to the previous section and compare your initial ideas with the discussion. How much of your initial ideas are found in the discussion? Which ideas are different and need revision? Now that you know the important ideas about this topic, let's go deeper by moving on to the next section. Area = 169 cm2 s s Area = 256 cm2 s s 5 cm 5 cm
30. DRAFT March 24, 2014 27 What to REFLECT ON and FURTHER UNDERSTAND: Activity 8: Extract Then Describe Me! Directions: Solve each of the following quadratic equations by extracting square roots. Answer the questions that follow. 1. 123 2 t 4. 1502 x 2. 072 x 5. 16 92 x 3. 183 2 r 6.   0814 2 s Questions: a. How did you find the roots of each equation? b. Which equation did you find difficult to solve by extracting square roots? Why? c. Which roots are rational? Which are not? Explain your answer. d. How will you approximate those roots that are irrational? Activity 9: Intensify Your Understanding! Directions: Answer the following. 1. Do you agree that a quadratic equation has at most two solutions? Justify your answer and give examples. 2. Give examples of quadratic equations with (a) two real solutions, (b) one real solution, and (c) no real solution. 3. Sheryl says that the solutions of the quadratic equations 492 w and 0492 w are the same. Do you agree with Sheryl? Justify your answer. Your goal in this section is to take a closer look at some aspects of the topic. You are going to think deeper and test further your understanding of solving quadratic equations by extracting square roots. After doing the following activities, you should be able to answer this important question: How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? Were you able to find and describe the roots of each equation? Were you able to approximate the roots that are irrational? I'm sure you did! Deepen further your understanding of solving quadratic equations by extracting square roots by doing the next activity.
31. DRAFT March 24, 2014 28 4. Mr. Cruz asked Emilio to construct a square table such that its area is 3 m2. Is it possible for Emilio to construct such table using an ordinary tape measure? Explain your answer. 5. A 9 ft.2 square painting is mounted with border on a square frame. If the total area of the border is 3.25 ft.2, what is the length of a side of the frame? In this section, the discussion was about your understanding of solving quadratic equations by extracting square roots. What new realizations do you have about solving quadratic equations by extracting square roots? How would you connect this to real life? How would you use this in making decisions? Now that you have a deeper understanding of the topic, you are ready to do the tasks in the next section.
32. DRAFT March 24, 2014 29 What to TRANSFER: Activity 10: What More Can I Do? Directions: Answer the following. 1. Describe quadratic equations with 2 solutions, 1 solution, and no solution. Give at least two examples for each. 2. Give at least five quadratic equations which can be solved by extracting square roots, then solve. 3. Summary/Synthesis/Generalization: Your goal in this section is to apply your learning to real-life situations. You will be given a practical task in which you will demonstrate your understanding of solving quadratic equations by extracting square roots. How did you find the performance task? How did the task help you see the real world use of the topic? Collect square tiles of different sizes. Using these tiles, formulate quadratic equations that can be solved by extracting square roots. Find the solutions or roots of these equations. This lesson was about solving quadratic equations by extracting square roots. The lesson provided you with opportunities to describe quadratic equations and solve these by extracting square roots. You were also able to find out how such equations are illustrated in real life. Moreover, you were given the chance to demonstrate your understanding of the lesson by doing a practical task. Your understanding of this lesson and other previously learned mathematics concepts and principles will enable you to learn about the wide applications of quadratic equations in real life.
33. DRAFT March 24, 2014 30 LEARNING MODULE MATH 9 LESSON NO. 2B: SOLVING QUADRATIC EQUATIONS BY FACTORING What to KNOW: Activity 1: What Made Me? Directions: Factor each of the following polynomials. Answer the questions that follow. 1. xx 82 2  6. 21102  xx 2. ss 93 2  7. 652  xx 3. 2 204 xx  8. 25204 2  rr 4. 2 105 tt  9. 49 2 t 5. 1282  ss 10. 1432 2  xx Questions: a. How did you factor each polynomial? b. What factoring technique did you use to come up with the factors of each polynomial? Explain how you used this technique. c. How would you know if the factors you got are the correct ones? d. Which of the polynomials did you find difficult to factor? Why? Start Lesson 2B of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in understanding solving quadratic equations by factoring. As you go through this lesson, think of this important question: "How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your answers with your teacher.
34. DRAFT March 24, 2014 31 Activity 2: The Manhole Directions: Use the situation below to answer the questions that follow. 1. Draw a diagram to illustrate the given situation. 2. How are you going to represent the length and the width of the pathway? How about its area? 3. What expression would represent the area of the cemented portion of the pathway? 4. Suppose the area of the cemented portion of the pathway is 19.5 m2. What equation would describe its area? 5. How will you find the length and the width of the pathway? How did you find the activity? Were you able to recall and apply the different mathematics concepts or principles in factoring polynomials? I'm sure you were. In the next activity, you will be representing a situation using a mathematical sentence. This mathematical sentence will be used to satisfy the conditions of the given situation. A rectangular metal manhole with an area of 0.5 m2 is situated along a cemented pathway. The length of the pathway is 8 m longer than its width. The activity you have just done shows how a real-life situation can be represented by a mathematical sentence. Were you able to represent the given situation by an equation? Do you now have an idea on how to use the equation in finding the length and the width of the pathway? To further give you ideas in solving the equation or other similar equations, perform the next activity.
35. DRAFT March 24, 2014 32 Activity 3: Why is the Product Zero? Directions: Use the equations below to answer the following questions. 1. How would you compare the three equations? 2. What value(s) of x would make each equation true? 3. How would you know if the value of x that you got satisfies each equation? 4. Compare the solutions of the given equations. What statement can you make? 5. Are the solutions of x + 7 = 0 and x – 4 = 0 the same as the solutions of (x + 7)(x – 4) = 0? Why? 6. How would you interpret the meaning of the equation (x + 7)(x – 4) = 0? Some quadratic equations can be solved easily by factoring. To solve such quadratic equations, the following procedure can be followed. 1. Transform the quadratic equation into standard form if necessary. 2. Factor the quadratic expression. 3. Apply the zero product property by setting each factor of the quadratic expression equal to 0. How did you find the preceding activities? Are you ready to learn about solving quadratic equations by factoring? I'm sure you are!!! From the activities done, you were able to find the factors of polynomials, represent a real-life situation by a mathematical statement, and interpret zero product. But how does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? You will find these out in the activities in the next section. Before doing these activities, read and understand first some important notes on solving quadratic equations by factoring and the examples presented. x + 7 = 0 x – 4 = 0 (x + 7)(x – 4) = 0 Zero Product Property If the product of two real numbers is zero, then either of the two is equal to zero or both numbers are equal to zero.
36. DRAFT March 24, 2014 33 4. Solve each resulting equation. 5. Check the values of the variable obtained by substituting each in the original equation. Example 1: Find the solutions of x2 + 9x = -8 by factoring. a. Transform the equation into standard form ax2 + bx + c = 0. x2 + 9x = -8  x2 + 9x + 8 = 0 b. Factor the quadratic expression x2 + 9x + 8. x2 + 9x + 8 = 0  (x + 1)(x + 8) = 0 c. Apply the zero product property by setting each factor of the quadratic expression equal to 0. (x + 1)(x + 8) = 0  x + 1 = 0; x + 8 = 0 d. Solve each resulting equation. x + 1 = 0  x + 1 – 1 = 0 – 1 x = -1 x + 8 = 0  x + 8 – 8 = 0 – 8 x = -8 e. Check the values of the variable obtained by substituting each in the equation x2 + 9x = -8. Both values of x satisfy the given equation. So the equation 892  xx is true when x = -1 or when x = -8. Answer: The equation 892  xx has two solutions: x = -1 or x = -8 For x = -1: 892  xx     8191 ? 2  891 ?  88  For x = -8: 892  xx     8898 ? 2  87264 ?  88 
37. DRAFT March 24, 2014 34 Example 2: Solve 9x2 – 4 = 0 by factoring. To solve the equation, factor the quadratic expression 9x2 – 4. 9x2 – 4 = 0  (3x + 2)(3x – 2) = 0 Set each factor to 0. 3x + 2 = 0; 3x – 2 = 0 Solve each resulting equation. Check the values of the variable obtained by substituting each in the equation 9x2 – 4 = 0. Both values of x satisfy the given equation. So the equation 049 2 x is true when 3 2- x or when 3 2 x . Answer: The equation 049 2 x has two solutions: 3 2- x or 3 2 x For 3 2- x : 049 2 x ?2 04 3 2 9        ? 04 9 4 9       ? 044  00  For 3 2 x : 049 2 x ?2 04 3 2 9       ? 04 9 4 9       ? 044  00  3x + 2 = 0  3x + 2 – 2 = 0 – 2 3x = -2 3 2 3 3  = x 3 2 x 3x – 2 = 0  3x – 2 + 2 = 0 + 2 3x = 2 3 2 = 3 3x 3 2 x
38. DRAFT March 24, 2014 35 What to PROCESS: Activity 4: Factor Then Solve! Directions: Solve the following quadratic equations by factoring. Answer the questions that follow. 1. 072  xx 6. xx 5142  2. 0186 2  ss 7. 2 21511 rr  3. 01682  tt 8. 0252 x 4. 025102  xx 9. 0481 2  x 5. 1662  hh 10. ss 1294 2  Questions: d. How did you find the solutions of each equation? e. What mathematics concepts or principles did you apply in finding the solutions? Explain how you applied these. f. Compare your answers with those of your classmates. Did you arrive at the same solutions? If NOT, explain. Your goal in this section is to apply previously learned mathematics concepts and principles in solving quadratic equations by factoring. Use the mathematical ideas and the examples presented in the preceding section to answer the activities provided. Learn more about Solving Quadratic Equations by Factoring through the WEB. You may open the following links. http://2012books.lardbucket.org/books/begi nning-algebra/s09-06-solving-equations- by-factoring.html http://www.purplemath.com/modules/solvq uad.htm http://www.webmath.com/quadtri.html http://www.mathwarehouse.com/quadratic/ solve-quadratic-equation-by-factoring.php
39. DRAFT March 24, 2014 36 Activity 5: What Must Be My Length and Width? Directions: The quadratic equation given describes the area of the shaded region of each figure. Use the equation to find the length and width of the figure. Answer the questions that follow. 2. 2. Questions: a. How did you find the length and width of each figure? b. Can all solutions to each equation be used to determine the length and width of each figure? Explain your answer. What to REFLECT ON and FURTHER UNDERSTAND: Your goal in this section is to take a closer look at some aspects of the topic. You are going to think deeper and test further your understanding of solving quadratic equations by factoring. After doing the following activities, you should be able to answer this important question: How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? Was it easy for you to find the solutions of quadratic equations by factoring? Did you apply the different mathematics concepts and principles in finding the solutions of each equation? I know you did! In this section, the discussion was about solving quadratic equations by factoring. Go back to the previous section and compare your initial ideas with the discussion. How much of your initial ideas are found in the discussion? Which ideas are different and need revision? Now that you know the important ideas about this topic, let's go deeper by moving on to the next section. (s + 6)(s – 2) = 153 (2s + 3)(s + 4) = 228s s 2 4 s 6 2s 3
40. DRAFT March 24, 2014 37 Activity 6: How Well Did I Understand? Directions: Answer each of the following. 1. Which of the following quadratic equations may be solved more appropriately by factoring? Explain your answer. a. 722 2 x c. 0642 w b. 036122  tt d. 01082 2  ss 2. Patricia says that it's more appropriate to use the method of factoring than extracting square roots in solving the quadratic equation 4x2 – 9 = 0. Do you agree with Patricia? Explain your answer. 3. Do you agree that not all quadratic equations can be solved by factoring? Justify your answer by giving examples. 4. Find the solutions of each of the following quadratic equations by factoring. Explain how you arrived at you answer. a. (x + 3)2 = 25 c. (2t – 3)2 = 2t2 + 5t – 26 b. (s + 4)2 = -2s d. 3(x + 2)2 = 2x2 + 3x – 8 5. Do you agree that x2 + 5x – 14 = 0 and 14 – 5x – x2 = 0 have the same solutions? Justify your answer. 6. Show that the equation (x – 4)2 = 9 can be solved both by factoring and extracting square roots. 7. A computer manufacturing company would like to come up with a new laptop computer such that its monitor is 80 square inches smaller than the present ones. Suppose the length of the monitor of the larger computer is 5 inches longer than its width and the area of the smaller computer is 70 square inches. What are the dimensions of the monitor of the larger computer? In this section, the discussion was about your understanding of solving quadratic equations by factoring. What new insights do you have about solving quadratic equations by factoring? How would you connect this to real life? How would you use this in making decisions? Now that you have a deeper understanding of the topic, you are ready to do the tasks in the next section.
41. DRAFT March 24, 2014 38 What to TRANSFER: Activity 7: Meet My Demands!!! Directions: Answer the following. Mr. Lakandula would like to increase his production of milkfish (bangus) due to its high demand in the market. He is thinking of making a larger fishpond in his 8000 sq m lot near a river. Help Mr. Lakandula by making a sketch plan of the fishpond to be made. Out of the given situation and the sketch plan made, formulate as many quadratic equations then solve by factoring. You may use the rubric in the next page to rate your work. Rubric for Sketch Plan and Equations Formulated and Solved 4 3 2 1 The sketch plan is accurately made, presentable, and appropriate. The sketch plan is accurately made and appropriate. The sketch plan is not accurately made but appropriate. The sketch plan is made but not appropriate. Quadratic equations are accurately formulated and solved correctly. Quadratic equations are accurately formulated but not all are solved correctly. Quadratic equations are accurately formulated but are not solved correctly. Quadratic equations are accurately formulated but are not solved. Summary/Synthesis/Generalization: Your goal in this section is to apply your learning to real-life situations. You will be given a practical task which will demonstrate your understanding of solving quadratic equations by factoring. This lesson was about solving quadratic equations by factoring. The lesson provided you with opportunities to describe quadratic equations and solve these by factoring. You were able to find out also how such equations are illustrated in real life. Moreover, you were given the chance to demonstrate your understanding of the lesson by doing a practical task. Your understanding of this lesson and other previously learned mathematics concepts and principles will facilitate your learning of the wide applications of quadratic equations in real life. How did you find the performance task? How did the task help you see the real world use of the topic?
42. DRAFT March 24, 2014 39 LEARNING MODULE MATH 9 LESSON NO. 2C: SOLVING QUADRATIC EQUATIONS BY COMPLETING THE SQUARE What to KNOW: Activity 1: How Many Solutions Do I Have? Directions: Find the solution/s of each of the following equations. Answer the questions that follow. 1. 1712 x 6. 2 1 4 3 x 2. 915 s 7.   3610 2 x 3. 1225 r 8.   129 2 w 4. 3 6 5 x 9. 16 9 2 1 2       k 5. 5 7 4 t 10. 2 1 5 3 2       h Start Lesson 2C of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in understanding Solving Quadratic Equations by Completing the Square. As you go through this lesson, think of this important question: "How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your answers with your teacher.
43. DRAFT March 24, 2014 40 Questions: a. How did you find the solution(s) of each equation? b. Which of the equations has only one solution? Why? c. Which of the equations has two solutions? Why? d. Which of the equations has solutions that are irrational? Why? e. Were you able to simplify those solutions that are irrational? Why? f. How did you write those irrational solutions? Activity 2: Perfect Square Trinomial to Square of a Binomial Directions: Express each of the following perfect square trinomials as a square of a binomial. Answer the questions that follow. 1. 442  xx 6. 81182  xx 2. 36122  tt 7. 9 1 3 22  tt 3. 25102  ss 8. 4 49 72  rr 4. 64162  xx 9. 64 9 4 32  ss 5. 49142  hh 10. 4 25 52  ww How did you find the activity? Were you able to recall and apply the different mathematics concepts or principles in finding the solution/s of each equation? I'm sure you did! In the next activity, you will be expressing a perfect square trinomial as a square of a binomial. I know that you already have an idea on how to do this. This activity will help you in solving quadratic equations by completing the square.
44. DRAFT March 24, 2014 41 Questions: a. How do you describe a perfect square trinomial? b. How did you express each perfect square trinomial as the square of a binomial? c. What mathematics concepts or principles did you apply to come up with your answer? Explain how you applied these. d. Compare your answer with those of your classmates. Did you get the same answer? If NOT, explain. e. Observe the terms of each trinomial. How is the third term related to the coefficient of the middle term? f. Is there an easy way of expressing a perfect square trinomial as a square of a binomial? If there is any, explain how. Activity 3: Make It Perfect!!! Directions: Determine a number that must be added to make each of the following a perfect square trinomial. Explain how you arrived at your answer. 1. ____22  xx 6. ____112  xx 2. ____202  tt 7. ____152  xx 3. ____162  rr 8. ____212  ww 4. ____242  rr 9. ____ 3 22  ss 5. ____302  xx 10. ____ 4 32  hh Were you able to express each perfect square trinomial as a square of a binomial? I'm sure you did! Let us further strengthen your knowledge and skills in mathematics particularly in writing perfect square trinomials by doing the next activity. Was it easy for you to determine the number that must be added to the terms of a polynomial to make it a perfect square trinomial? Were you able to figure out how it can be easily done? In the next activity, you will be representing a situation using a mathematical sentence. Such a mathematical sentence will be used to satisfy the conditions of the given situation.
45. DRAFT March 24, 2014 42 Activity 4: Finish the Contract! Extracting square roots and factoring are usually used to solve quadratic equations of the form 02  cax . If the factors of the quadratic expression of 02  cbxax are determined, then it is more convenient to use factoring to solve it. Another method of solving quadratic equation is by completing the square. This method involves transforming the quadratic equation ax2 + bx + c = 0 into the form (x – h)2 = k, where k ≥ 0. Can you tell why the value of k should be positive? To solve the quadratic equation ax2 + bx + c = 0 by completing the square, the following steps can be followed: 1. Divide both sides of the equation by a then simplify. 2. Write the equation such that the terms with variables are on the left side of the equation and the constant term is on the right side. How did you find the preceding activities? Are you ready to learn about solving quadratic equations by completing the square? I'm sure you are!!! From the activities done, you were able to solve equations, express a perfect square trinomial as a square of a binomial, write perfect square trinomials, and represent a real-life situation by a mathematical sentence. But how does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? You will find these out in the activities in the next section. Before doing these activities, read and understand first some important notes on Solving Quadratic Equations by Completing the Square and the examples presented. Directions: The shaded region of the diagram at the right shows the portion of a square-shaped car park that is already cemented. The area of the cemented part is 600 m2. Use the diagram to answer the following questions. 1. How would you represent the length of the side of the car park? How about the width of the cemented portion? 2. What equation would represent the area of the cemented part of the car park? 3. Using the equation formulated, how are you going to find the length of a side of the car park? 10 m 10 m
46. DRAFT March 24, 2014 43 3. Add the square of one-half of the coefficient of x on both sides of the resulting equation. The left side of the equation becomes a perfect square trinomial. 4. Express the perfect square trinomial on the left side of the equation as a square of a binomial. 5. Solve the resulting quadratic equation by extracting the square root. 6. Solve the resulting linear equations. 7. Check the solutions obtained against the original equation. Example 1: Solve the quadratic equation 2x2 + 8x – 10 = 0 by completing the square. Divide both sides of the equation by 2 then simplify. 2x2 + 8x – 10 = 0  2 0 2 1082 2   xx x2 + 4x – 5= 0 Add 5 to both sides of the equation then simplify. x2 + 4x – 5= 0  x2 + 4x – 5 + 5 = 0 + 5 x2 + 4x = 5 Add to both sides of the equation the square of one-half of 4. x2 + 4x = 5  x2 + 4x + 4 = 5 + 4 x2 + 4x + 4 = 9 Express x2 + 4x + 4 as a square of a binomial. x2 + 4x + 4 = 9  (x + 2)2 = 9 Solve (x + 2)2 = 9 by extracting the square root. (x + 2)2 = 9  92 x x + 2 = ±3 Solve the resulting linear equations. x + 2 = 3 x + 2 – 2 = 3 – 2 x = 1 x + 2 = -3 x + 2 – 2 = -3 – 2 x = -5   24 2 1   22 = 4
47. DRAFT March 24, 2014 44 Check the solutions obtained against the original equation 2x2 + 8x – 10 = 0. Both values of x satisfy the given equation. So the equation 01082 2  xx is true when x = 1 or when x = -5. Answer: The equation 01082 2  xx has two solutions: x = 1 or x = -5 Example 2: Find the solutions of the equation 01832  xx by completing the square. Add 18 to both sides of the equation then simplify. 01832  xx  180181832  xx 1832  xx Add to both sides of the equation the square of one-half of 3. 1832  xx  4 9 18 4 9 32  xx 4 9 4 72 4 9 32  xx  4 81 4 9 32  xx Express 4 9 32  xx as a square of a binomial. 4 81 4 9 32  xx  4 81 2 3 2       x Solve 4 81 2 3 2       x by extracting the square root. For x = 1: 01082 2  xx     ? 2 0101812    ? 010812  ? 01082  00  For x = -5: 01082 2  xx     ? 2 0105852    ? 01040252  ? 0104050  00    2 3 3 2 1   4 9 2 3 2      
48. DRAFT March 24, 2014 45 4 81 2 3 2       x  4 81 2 3 x 2 9 2 3 x Solve the resulting linear equations. Check the solutions obtained against the equation 01832  xx . Both values of x satisfy the given equation. So the equation 01832  xx is true when x = 3 or when x = -6. Answer: The equation 01832  xx has two solutions: x = 3 or x = -6 Example 3: Find the solutions of x2 – 6x – 41 = 0 by completing the square. Add 41 to both sides of the equation then simplify. x2 – 6x – 41 = 0  x2 – 6x – 41 + 41 = 0 + 41 x2 – 6x = 41 2 6 2 3 2 9 2 3 2 3 2 9 2 3    x x x x = 3 2 12 2 3 2 9 2 3 2 3 2 9 2 3    x x x x = -6 For x = 3: 01832  xx     ? 2 018333  ? 01899  00  For x = -6: 01832  xx     ? 2 018636  ? 0181836  00 
49. DRAFT March 24, 2014 46 Add to both sides of the equation the square of one-half of -6. x2 – 6x = 41  x2 – 6x + 9 = 41 + 9 x2 – 6x + 9 = 50 Express x2 – 6x + 9 as a square of a binomial. x2 – 6x + 9 = 50  (x – 3)2 = 50 Solve (x – 3)2 = 50 by extracting the square root. (x – 3)2 = 50  503 x Hence, 503 x is the same as 253 x . Solve the resulting linear equations. Check the solutions obtained against the equation x2 – 6x – 41 = 0. 253 x 32533 x 253 x For 253 x : 04162  xx     0412536253 ?2  04123018502309 ?  00    36 2 1   (-3)2 = 9 253 x 32533 x 253 x 50 can be expressed as 225  or 225  . Notice that 25 is a perfect square. So, 225  can be simplified further to 25 .
50. DRAFT March 24, 2014 47 Both values of x satisfy the given equation. So the equation 04062  xx is true when 253 x or when 253 x . Answer: The equation 04062  xx has two solutions: 253 x or 253 x What to PROCESS: Your goal in this section is to apply the key concepts of solving quadratic equations by completing the square. Use the mathematical ideas and the examples presented in the preceding section to answer the activities provided. Learn more about Solving Quadratic Equations by Completing the Square through the WEB. You may open the following links. http://www.purplemath.com/modules/sqrqu ad.htm http://2012books.lardbucket.org/books/begi nning-algebra/s12-02-completing-the- square.html http://www.regentsprep.org/Regents/math/a lgtrig/ATE12/indexATE12.htm http://www.mathsisfun.com/algebra/complet ing-square.html For 253 x : 04162  xx     0412536253 ?2  04123018502309 ?  00 
51. DRAFT March 24, 2014 48 Activity 5: Complete Me! Directions: Find the solutions of each of the following quadratic equations by completing the square. Answer the questions that follow. 1. x2 – 2x = 3 6. 4x2 – 32x = -28 2. s2 + 4s – 21 = 0 7. 0652  xx 3. t2 + 10t + 9 = 0 8. 0 4 51 72  mm 4. x2 + 14x = 32 9. r2 + 4r = -1 5. r2 – 10r = -17 10. w2 + 6w – 11 = 0 Questions: a. How did you find the solutions of each equation? b. What mathematics concepts or principles did you apply in finding the solutions? Explain how you applied these. c. Compare your answers with those of your classmates. Did you arrive at the same answers? If NOT, explain. Was it easy for you to find the solutions of quadratic equations by completing the square? Did you apply the different mathematics concepts and principles in finding the solutions of each equation? I know you did!
52. DRAFT March 24, 2014 49 Activity 6: Represent then Solve! Directions: Using each figure, write a quadratic equation that represents the area of the shaded region. Then find the solutions to the equation by completing the square. Answer the questions that follow. 1. 2. Questions: a. How did you come up with the equation that represents the area of each shaded region? b. How did you find the solution/s of each equation? c. Do all solutions to each equation represent a particular measure of each figure? Explain your answer. Now that you know the important ideas about this topic, let's go deeper by moving on to the next section. Area = 88 cm2 3 cm s s 5 cm Area = 176 cm2 t t Were you able to come up with the right representations of the area of the shaded region of each figure? Were you able to solve the equations formulated and obtain the appropriate measure that would describe each figure? In this section, the discussion was about solving quadratic equations by completing the square. Go back to the previous section and compare your initial ideas with the discussion. How much of your initial ideas are found in the discussion? Which ideas are different and need revision?
53. DRAFT March 24, 2014 50 What to REFLECT ON and FURTHER UNDERSTAND: Activity 7: What Solving Quadratic Equations by Completing the Square Means to Me… Directions: Answer the following. 1. Karen wants to use completing the square in solving the quadratic equation 4x2 – 25 = 0. Can she use it in finding the solutions of the equation? Explain why or why not. 2. Do you agree that any quadratic equation can be solved by completing the square? Justify your answer. 3. If you are to choose between completing the square and factoring in finding the solutions of each of the following equations, which would you choose? Explain and solve the equation using your preferred method. a. 4x2 – 20x = 11 b. x2 + 7x + 12 = 0 4. Gregorio solved the equation 2x2 – 8x + 15 = 0. The first few parts of his solution are shown below. 2x2 – 8x + 15 = 0  2x2 – 8x + 15 – 15 = 0 – 15 2x2 – 8x = –15 2x2 – 8x + 16 = –15 + 16 Do you think Gregorio arrived at the correct solutions of the equation? Justify your answer. 5. An open box is to be formed out of a rectangular piece of cardboard whose length is 8 cm longer than its width. To form the box, a square of side 4 cm will be removed from each corner of the cardboard. Then the edges of the remaining cardboard will be turned up. a. Draw a diagram to illustrate the given situation. b. How would you represent the dimensions of the cardboard? c. What expressions represent the length, width, and height of the box?   48 2 1  ; (-4)2 = 16 Your goal in this section is to take a closer look at some aspects of the topic. You are going to think deeper and test further your understanding of solving quadratic equations by completing the square. After doing the following activities, you should be able to answer this important question: How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions?
54. DRAFT March 24, 2014 51 d. If the box is to hold 448 cm3, what mathematical sentence would represent the given situation? e. Using the mathematical sentence formulated, how are you going to find the dimensions of the rectangular piece of cardboard? f. What are the dimensions of the rectangular piece of cardboard? g. What is the length of the box? How about its width and height? 6. From 2006 through 2012, the average weekly income of an employee in a certain company is estimated by the quadratic expression 324048.618.0 2  nn , where n is the number of years after 2006. In what year did the average weekly income of an employee become Php3268.80? What to TRANSFER: Activity 8: Design Packaging Boxes!!! Directions: Perform the following. A. Designing Open Boxes 1. Make sketch plans of 5 rectangular open boxes such that: a. the heights of the boxes are the same; and b. the boxes can hold 240 cm3, 270 cm3, 504 cm3, 810 cm3, and 468 cm3, respectively. 2. Write a quadratic equation that would represent the volume of each box. Your goal in this section is to apply your learning to real-life situations. You will be given a practical task which will demonstrate your understanding of solving quadratic equations by completing the square. In this section, the discussion was about your understanding of solving quadratic equations by completing the square. What new insights do you have about solving quadratic equations by completing the square? How would you connect this to real life? How would you use this in making decisions? Now that you have a deeper understanding of the topic, you are ready to do the tasks in the next section.
55. DRAFT March 24, 2014 52 3. Solve each quadratic equation by completing the square to determine the dimensions of the materials to be used in constructing each box. B. Designing Covers of the Open Boxes 1. Make sketch plans of covers of the open boxes in Part A such that: a. the heights of the covers are the same; and b. the base of each cover is rectangular. 2. Write a quadratic equation that would represent the volume of the box's cover. 3. Solve each quadratic equation by completing the square to determine the dimensions of the materials to be used in constructing the box's cover. Rubric for Sketch Plan and Equations Formulated and Solved 4 3 2 1 The sketch plan is accurately made, presentable, and appropriate. The sketch plan is accurately made and appropriate. The sketch plan is not accurately made but appropriate. The sketch plan is made but not appropriate. Quadratic equations are accurately formulated and solved correctly. Quadratic equations are accurately formulated but not all are solved correctly. Quadratic equations are accurately formulated but are not solved correctly. Quadratic equations are accurately formulated but are not solved. Summary/Synthesis/Generalization: How did you find the performance task? How did the task help you see the real world use of the topic? This lesson was about solving quadratic equations by completing the square. The lesson provided you with opportunities to describe quadratic equations and solve these by completing the square. You were able to find out also how such equations are illustrated in real life. Moreover, you were given the chance to demonstrate your understanding of the lesson by doing a practical task. Your understanding of this lesson and other previously learned mathematics concepts and principles will facilitate your learning of the wide applications of quadratic equations in real life.
56. DRAFT March 24, 2014 53 LEARNING MODULE MATH 9 LESSON NO. 2D: SOLVING QUADRATIC EQUATIONS BY USING THE QUADRATIC FORMULA What to KNOW: Activity 1: It's Good to be Simple! Directions: Work with a partner in simplifying each of the following expressions. Answer the questions that follow. 1. )3(2 96  6. )1(2 20366  2. )3(2 96  7. )4(2 100255  3. )2(2 186  8. )3(2 521010 2  4. )2(2 249  9. )4(2 1644 2  5. )3(2 28648   10. )3(2 )2)(3(455 2  Start Lesson 2D of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in understanding solving quadratic equations by using the quadratic formula. As you go through this lesson, think of this important question: "How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your answers with your teacher.
57. DRAFT March 24, 2014 54 Questions: a. How would you describe the expressions given? b. How did you simplify each expression? c. Which expression did you find difficult to simplify? Why? d. Compare your work with those of your classmates. Did you arrive at the same answer? Activity 2: Follow the Standards! Directions: Write the following quadratic equations in standard form, ax2 + bx + c = 0. Then identify the values of a, b, and c. Answer the questions that follow. 1. 2x2 + 9x =10 6. x(5 – 2x) + 15 = 0 2. -2x2 = 2 – 7x 7. (x + 4)(x + 12) = 0 3. 6x – 1 = 2x2 8. (x – 6)(x – 9) = 0 4. 10 + 7x – 3x2 = 0 9. (3x + 7)(x – 1) = 0 5. 2x(x – 6) = 5 10. 3(x – 5)2 + 10 = 0 Questions: a. How did you write each quadratic equation in standard form? b. How do you describe a quadratic equation that is written in standard form? c. Are there different ways of writing a quadratic equation in standard form? Justify your answer. How did you find the activity? Were you able to simplify the expressions? I'm sure you did! In the next activity, you will be writing quadratic equations in standard form. You need this skill for you to solve quadratic equations by using the quadratic formula. Were you able to write each quadratic equation in standard form? Were you able to determine the values of a, b, and c? If you did, then extend further your understanding of the real-life applications of quadratic equations by doing the next activity.
58. DRAFT March 24, 2014 55 Activity 3: Why do the Gardens Have to be Adjacent? Directions: Use the situation below to answer the questions that follow. 1. How would you represent the dimensions of each garden? 2. What mathematical sentence would represent the length of fencing material to be used in enclosing the two gardens? How about the mathematical sentence that would represent the total area of the two gardens? 3. How will you find the dimensions of each garden? 4. What equation will you use in finding the dimensions of each garden? 5. How would you describe the equation formulated in item 4? How are you going to find the solutions of this equation? 6. Do you think the methods of solving quadratic equations that you already learned can be used to solve the equation formulated in item 4? Why? Mr. Bonifacio would like to enclose his two adjacent rectangular gardens with 70.5 m of fencing materials. The gardens are of the same size and their total area is 180 m2. Did the activity you just performed capture your interest? Were you able to formulate mathematical sentence that will lead you in finding the measures of the unknown quantities? In the next activity, you will be given the opportunity to derive a general mathematical sentence which you can use in solving quadratic equations.
59. DRAFT March 24, 2014 56 Activity 4: Lead Me to the Formula! Directions: Work in groups of 4 in finding the solutions of the following quadratic equation by completing the square. Answer the questions that follow. 1. How did you use completing the square in solving the given equation? Show the complete details of your work. 2. What are the solutions of the given equation? 3. How would you describe the solutions obtained? 4. Compare your work with those of other groups. Did you obtain the same solutions? If NOT, explain. 5. In the equation 2x2 + 9x + 10 = 0, what would be the resulting equation if 2, 9, and 10 were replaced by a, b, and c, respectively? 6. Using the resulting equation in item 5, how are you going to find the value of x if you follow the same procedure in finding the solutions of 2x2 + 9x + 10 = 0? What equation or formula would give the value of x? 7. Do you think the equation or formula that would give the value of x can be used in solving other quadratic equations? Justify your answer by giving examples. 2x2 + 9x + 10 = 0 How did you find the preceding activities? Are you ready to learn about solving quadratic equations by using the quadratic formula? I'm sure you are!!! From the activities done, you were able to solve equations, express a perfect square trinomial as a square of a binomial, write perfect square trinomials, and represent a real-life situation by a mathematical sentence. But how does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? You will find these out in the activities in the next section. Before doing these activities, read and understand first some important notes on Solving Quadratic Equations by using the Quadratic Formula and the examples presented.
60. DRAFT March 24, 2014 57 The solutions of any quadratic equation ax2 + bx + c = 0 can be determined using the quadratic formula 2a 4acbb 2  x , a ≠ 0. This formula can be derived by applying the method of completing the square as shown on the next page. ax2 + bx + c = 0  ax2 + bx = -c Why? a c a ba 2    xx  a c a b2   x x Why? 2a b a b 2 1       ; 2 22 4a b 2a b       Why? 2 2 2 2 2 4a b a c 4a b a b    x x Why? 2 2 2 22 4a 4acb 4a b4ac 2a b          x Why? 2 2 4a 4acb 2a b  x  2a 4acb 2a b 2  x Why? 2a b 2a 4acb2   x Why? 2a 4acbb 2  x Why? To solve any quadratic equation ax2 + bx + c = 0 using the quadratic formula, determine the values of a, b, and c, then substitute these in the equation 2a 4acbb 2  x . Simplify the result if possible then check the solutions obtained against the original equation. Example 1: Find the solutions of the equation 2x2 + 3x = 27 using the quadratic formula. Write the equation in standard form. 2x2 + 3x = 27 2x2 + 3x – 27 = 0 Determine the values of a, b, and c. 2x2 + 3x – 27 = 0  a = 2; b = 3; c = -27 Substitute the values of a, b, and c in the quadratic formula.
61. DRAFT March 24, 2014 58 2a 4acbb 2  x          22 27-2433 2  x Simplify the result.         22 27-2433 2  x  4 21693  x 4 2253  x 4 153  x Check the solutions obtained against the equation 2x2 + 3x = 27. When x = 3:     273332 ? 2       273392 ?  27918 ?  2727  When 2 9 x : 27 2 9 3 2 9 2 ?2               27 2 9 3 4 81 2 ?             27 2 27 2 81 ?  27 2 54 ?  2727  Both values of x satisfy the given equation. So the equation 2732 2  xx is true when x = 3 or when 2 9 x . 4 12 4 153   x x = 3 4 18 4 153    x 2 9 x
62. DRAFT March 24, 2014 59 Answer: The equation 2732 2  xx has two solutions: x = 3 or 2 9 x . What to PROCESS: Activity 5: Is the Formula Effective? Directions: Find the solutions of each of the following quadratic equations using the quadratic formula. Answer the questions that follow. 1. 09102  xx 6. 0972 2  xx 2. 035122  xx 7. 0144 2  xx 3. 01452  xx 8. 043 2  xx 4. 01242  xx 9. 0729 2 x 5. 472  xx 10. 342 2  xx Questions: a. How did you use the quadratic formula in finding the solution/s of each equation? b. How many solutions does each equation have? Learn more about Solving Quadratic Equations by Using the Quadratic Formula through the WEB. You may open the following links. http://2012books.lardbucket.org/books/begi nning-algebra/s12-03-quadratic- formula.html http://www.regentsprep.org/Regents/math/a lgtrig/ATE3/quadformula.htm http://www.purplemath.com/modules/quadf orm.htm http://www.algebrahelp.com/lessons/equati ons/quadratic/ Your goal in this section is to apply the key concepts of solving quadratic equations by using the quadratic formula. Use the mathematical ideas and the examples presented in the preceding section to answer the activities provided.
63. DRAFT March 24, 2014 60 c. Is there any equation whose solutions are equal? If there is any, describe the equation. d. Is there any equation with zero as one of the solutions? Describe the equation if there is any. e. Compare your answers with those of your classmates. Did you arrive at the same solutions? If NOT, explain. Activity 6: Cut to Fit! Directions: Read and understand the situation below then answer the questions that follow. Mr. Bonifacio cuts different sizes of rectangular plywood to be used in the furniture that he makes. Some of these rectangular plywood are described below. Plywood 1: The length of the plywood is twice its width and the area is 4.5 sq ft. Plywood 2: The length of the plywood is 1.4 ft. less than twice its width and the area is 16 sq ft. Plywood 3: The perimeter of the plywood is 10 ft. and its area is 6 sq ft. Questions: 1. What quadratic equation represents the area of each piece of plywood? Write the equation in terms of the width of the plywood. 2. Write each quadratic equation formulated in item 1 in standard form. Then determine the values of a, b, and c. 3. Solve each quadratic equation using the quadratic formula. 4. Which of the solutions or roots obtained represents the width of each plywood? Explain your answer. 5. What is the length of each piece of plywood? Explain how you arrived at your answer. Was it easy for you to find the solutions of quadratic equations by using the quadratic formula? Were you able to simplify the solutions obtained? I know you did!
64. DRAFT March 24, 2014 61 What to REFLECT ON and FURTHER UNDERSTAND: Activity 7: Make the Most Out of It! Directions: Answer the following. 1. The values of a, b, and c of a quadratic equation written in standard form are -2, 8, and 3, respectively. Another quadratic equation has 2, -8, and -3 as the values of a, b, and c, respectively. Do you agree that the two equations have the same solutions? Justify your answer. 2. How are you going to use the quadratic formula in determining whether a quadratic equation has no real solutions? Give at least two examples of quadratic equations with no real solutions. 3. Find the solutions of the following quadratic equations using the quadratic formula. Tell whether the solutions are real numbers or not real numbers. Explain your answer. a. x2 + 2x + 9 = 0 c. (2x – 5)2 – 4 = 0 b. 2x2 + 4x + 7 = 0 d. (3x + 2)2 = 3x + 10 4. Do you think the quadratic formula is more appropriate to use in solving quadratic equations? Explain then give examples to support your answer. Your goal in this section is to take a closer look at some aspects of the topic. You are going to think deeper and test further your understanding of solving quadratic equations by using the quadratic formula. After doing the following activities, you should be able to answer this important question: How does finding solutions of quadratic equations facilitate in solving real-life problems and in making decisions? Now that you know the important ideas about this topic, let's go deeper by moving on to the next section. Were you able to come up with the quadratic equation that represents the area of each piece of plywood? Were you able to determine the length and width of each piece of plywood? In this section, the discussion was about solving quadratic equations by using the quadratic formula. Go back to the previous section and compare your initial ideas with the discussion. How much of your initial ideas are found in the discussion? Which ideas are different and need revision?
65. DRAFT March 24, 2014 62 5. If you are to solve each of the following quadratic equations, which method would you use and why? Explain your answer. a. 9x2 = 225 d. 2x2 + x – 28 = 0 b. 4x2 – 121 = 0 e. 4x2 + 16x + 15 = 0 c. x2 + 11x + 30 = 0 f. 4x2 + 4x – 15 = 0 6. The length of a car park is 120 m longer than its width. The area of the car park is 6400 m2. a. How would you represent the width of the car park? How about its length? b. What equation represents the area of the car park? c. How would you use the equation representing the area of the car park in finding its length and width? d. What is the length of the car park? How about its width? Explain how you arrived at your answer. e. Suppose the area of the car park is doubled, would its length and width also double? Justify your answer. 7. The length of a rectangular table is 0.6 m more than twice its width and its area is 4.6 m2. What are the dimensions of the table? 8. Grace constructed an open box with a square base out of 192 cm2 material. The height of the box is 4 cm. What is the length of the side of the base of the box? 9. A car travels 30 kph faster than a truck. The car covers 540 km in three hours less than the time it takes the truck to travel the same distance. What is the speed of the car? What about the truck? In this section, the discussion was about your understanding of solving quadratic equations by using the quadratic formula. What new insights do you have about solving quadratic equations by using the quadratic formula? How would you connect this to real life? How would you use this in making decisions? Now that you have a deeper understanding of the topic, you are ready to do the tasks in the next section.
66. DRAFT March 24, 2014 63 What to TRANSFER: Activity 8: Show Me The Best Floor Plan!!! Directions: Use the situation below to answer the questions that follow. Mr. Luna would like to construct a new house with a floor area of 72 m2. He asked an architect to prepare a floor plan that shows the following: c. 2 bedrooms d. Comfort room d. Living room e. Kitchen e. Dining room f. Laundry Area 1. Suppose you were the architect asked by Mr. Luna to prepare a floor plan. How will you do it? Draw the floor plan. 2. Formulate as many quadratic equations using the floor plan that you prepared. Solve the equations using the quadratic formula. Rubric for Sketch Plan and Equations Formulated and Solved 4 3 2 1 The sketch plan is accurately made, presentable, and appropriate. The sketch plan is accurately made and appropriate. The sketch plan is not accurately made but appropriate. The sketch plan is made but not appropriate. Quadratic equations are accurately formulated and solved correctly. Quadratic equations are accurately formulated but not all are solved correctly. Quadratic equations are accurately formulated but are not solved correctly. Quadratic equations are accurately formulated but are not solved. Your goal in this section is to apply your learning to real-life situations. You will be given a practical task which will demonstrate your understanding. How did you find the performance task? How did the task help you see the real world use of the topic?
67. DRAFT March 24, 2014 64 Summary/Synthesis/Generalization: This lesson was about solving quadratic equations by using the quadratic formula. The lesson provided you opportunities to describe quadratic equations and solve these by using the quadratic formula. You were able to find out also how such equations are illustrated in real life. Moreover, you were given the chance to demonstrate your understanding of the lesson by doing a practical task. Your understanding of this lesson and other previously learned mathematics concepts and principles will facilitate your learning of the wide applications of quadratic equations in real life.
68. DRAFT March 24, 2014 65 LEARNING MODULE MATH 9 LESSON NO. 3: THE NATURE OF THE ROOTS OF A QUADRATIC EQUATION What to KNOW: Activity 1: Which are Real? Which are Not? Directions: Refer to the numbers below to answer the questions that follow. I L O V E M A T H Start lesson 3 of this module by assessing your knowledge of the different mathematics concepts previously studied and your skills in performing mathematical operations. These knowledge and skills will help you in understanding the nature of roots of quadratic equations. As you go through this lesson, think of this important question: "How does the nature of roots of quadratic equation facilitate in understanding the conditions of real life situations?" To find the answer, perform each activity. If you find any difficulty in answering the exercises, seek the assistance of your teacher or peers or refer to the modules you have gone over earlier. You may check your answers with your teacher. 24. 5 289
69. DRAFT March 24, 2014 66 Questions: 1. Which of the numbers above are familiar to you? Why? Describe these numbers. 2. Which of the numbers are real? Which are not real? 3. Which of the numbers are rational? irrational? Explain your answer. 4. Which of the numbers are perfect squares? not perfect squares? 5. How do you describe numbers that are perfect squares? Activity 2: Math in A, B, C? Directions: Write the following quadratic equations in standard form, ax² + bx + c = 0, then identify the values of a, b, and c. Answer the questions that follow. ax² + bx + c = 0 1. x² + 5x = 4 _______________ a = ____ b = ____ c = _____ 2. -4x2 = 8x – 3 _______________ a = ____ b = ____ c = _____ 3. 10x – 1 = 4x² _______________ a = ____ b = ____ c = _____ 4. 15 + 8x – 3x2 = 0 _______________ a = ____ b = ____ c = _____ 5. 3x(x – 14) = 12 _______________ a = ____ b = ____ c = _____ Questions: a. How did you write each quadratic equation in standard form? b. Aside from your answer, do you think there is another way of writing each quadratic equation in standard form? If YES, show then determine the values of a, b, and c. Were you able to classify the given numbers as real or not real, and as rational or irrational? In the next activity, you will determine the values of a, b, and c when the quadratic equation is written in the form ax² + bx + c = 0. You have done this activity in the previous lessons so I am sure you are already familiar with this. Were you able to rewrite the given quadratic equations in the form ax²+bx+c = 0? Were you able to find the value of a, b and c? In the next activity, you will find the value of b2 – 4ac. This value will be your basis in describing the roots of a quadratic equation.
70. DRAFT March 24, 2014 67 Activity 3: What's My Value? Directions: Evaluate the expression b² – 4ac given the following values of a, b, and c. 1. a = 1, b = 5, c = 4 2. a = 2, b = 1, c = -21 3. a = 4, b = 4, c = 1 4. a = 1, b = - 2, c = -2 5. a = 9, b = 0, c = 16 Activity 4: Find my Equation and Roots Directions: Using the values of a, b and c in Activity 3, write the quadratic equation ax² + bx + c = 0.Then find the roots of each resulting equation. ax² + bx +c = 0 Roots 1. _________________________ _________________ 2. _________________________ _________________ 3. _________________________ _________________ 4. _________________________ _________________ 5. _________________________ _________________ Were you able to evaluate the expression b2 – 4ac given the values of a, b and c? What do you think is the importance of the expression b2 – 4ac in determining the nature of the roots of quadratic equation? You will find this out as you perform the succeeding activities. Were you able to write the quadratic equation given the values of a, b and c? Were you able to find the roots of the resulting quadratic equation? In the next activity, you will describe the nature of the roots of quadratic equation using the value of b2 – 4ac.
71. DRAFT March 24, 2014 68 Activity 5: Place Me on the Table! Directions: Answer the following. 1. Complete the table below using your answers in activities 3 and 4. Equation b² - 4ac Roots 1. 2. 3. 4. 5. 2. How would you describe the roots of quadratic equation when the value of b2 – 4ac is 0? positive and perfect square? positive but not perfect square? negative? 3. Which quadratic equation has roots that are real numbers and equal? rational numbers? Irrational numbers? not real numbers? 4. How do you determine the quadratic equation having roots that are real numbers and equal? rational numbers? irrational numbers? not real numbers? Activity 6: Let's Shoot that Ball! Directions: Study the situation below and answer the questions that follow. A basketball player throws a ball vertically with an initial velocity of 100ft/sec. The distance of the ball from the ground after t seconds is given by the expression 100t – 16t². 1. What is the distance of the ball from the ground after 6 seconds? 2. After how many seconds does the ball reach a distance of 50 ft. from the ground? 3. How many seconds will it take for the ball to fall to the ground? 4. Do you think the ball can reach the height of 160 ft.? Why? Why not? Were you able to relate the value of b² - 4ac to the nature of the roots of the quadratic equation? In the next activity, you will find out how the discriminant of the quadratic equation is illustrated in real-life situations.
72. DRAFT March 24, 2014 69 The value of the expression b2 – 4ac is called the discriminant of the quadratic equation ax² + bx + c = 0. This value can be used to describe the nature of the roots of a quadratic equation. It can be zero, positive and perfect square, positive but not perfect square or negative. 1. When b2 – 4ac is equal to zero, then the roots are real numbers and are equal. Example: Describe the roots of 0442  xx . The values of a, b, and c in the equation are the following. a = 1 b = -4 c = 4 Substitute these values of a, b and c in the expression b² – 4ac.     4144ac4b 22  1616  0 Since the value of b2 – 4ac is zero, we can say that the roots of the quadratic equation 0442  xx are real numbers and are equal. This can be checked by determining the roots of 0442  xx using any of the methods of solving quadratic equation. How did you find the preceding activities? Are you ready to learn more about the nature of the roots of quadratic equations? From the activities you have done, you were able to determine the nature of roots of quadratic equations, whether they are real numbers, not real numbers, rational or irrational numbers. Moreover, you were able to find out how quadratic equations are illustrated in real life. Find out more about the applications of quadratic equations by performing the activities in the next section. Before doing these activities, read and understand first some important notes on Quadratic Equations and the examples presented.

Grade 9 Mathematics Learners Module Answer Key

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