Graphs of Nonlinear Inequalities

Transcription

1 3-3 BJECTIVES Graph polnomial, absolute value, and radical inequalities in two variables. Solve absolute value inequalities. Graphs of Nonlinear Inequalities PHARMACLGY Pharmacists label medication as to how much and how often it should be taken. Because oral medication requires time to take effect, the amount of medication in our bod varies with time. Suppose the equation m() for 0 6 models the number of milligrams of a certain pain reliever in the bloodstream hours after taking 400 milligrams of it. The medicine is to be taken ever 4 hours. At what times during the first 4-hour period is the level of pain reliever in the bloodstream above 300 milligrams? This problem will be solved in Eample 5. Real World A p plic atio n Problems like the one above can be solved b graphing inequalities. Graphing inequalities in two variables identifies all ordered pairs that will satisf the inequalit. Eample 1 Determine whether (3, 4), (4, 7), (1, 1), and ( 1, 6) are solutions for the inequalit ( 2) 2 3. Substitute the -value and -value from each ordered pair into the inequalit. Look Back Refer to Lesson 1-8 for more about graphing linear inequalities. ( 2) 2 3 4? (3 2) 2 3 (, ) (3, 4) 4 2 true ( 2) 2 3 7? (4 2) 2 3 (, ) (4, 7) 7 1 false ( 2) 2 3 1? (1 2) 2 3 (, ) (1, 1) 1 2 false ( 2) 2 3 6? ( 1 2) 2 3 (, ) ( 1, 6) 6 6 true f these ordered pairs, (3, 4) and ( 1, 6) are solutions for ( 2) 2 3. Similar to graphing linear inequalities, the first step in graphing nonlinear inequalities is graphing the boundar. You can use concepts from Lesson 3-2 to graph the boundar. Eample 2 Graph ( 4) 3 2. The boundar of the inequalit is the graph of ( 4) 3 2. To graph the boundar curve, start with the parent graph 3. Analze the boundar equation to determine how the boundar relates to the parent graph. ( 4) 3 2 move 4 units right move 2 units down Chapter 3 The Nature of Graphs

2 Graphing Calculator Appendi For kestroke instruction on how to graph inequalities see pages A13-A15. Since the boundar is included in the inequalit, the graph is drawn as a solid curve. The inequalit states that the -values of the solution are greater than the -values on the graph of ( 4) 3 2. For a particular value of, all of the points in the plane that lie above the curve have -values greater than ( 4) 3 2. So this portion of the graph should be shaded. ( 4) 3 2 To verif numericall, ou can test a point not on the boundar. It is common to test (0, 0) whenever it is not on the boundar. ( 4) 3 2 ( 4) 3 2 0? (0 4) 3 2 Replace (, ) with (0, 0) True Since (0, 0) satisfies the inequalit, the correct region is shaded. The same process used in Eample 2 can be used to graph inequalities involving absolute value. Eample 3 Graph 3 2. Begin with the parent graph. It is easier to sketch the graph of the given inequalit if ou rewrite it so that the absolute value epression comes first This more familiar form tells us the parent graph is reflected over the -ais and moved 2 units left and three units up. The boundar is not included, so draw it as a dashed line. The -values of the solution are greater than the -values on the graph of 3 2, so shade above the graph of 3 2. Verif b substituting (0, 0) in the inequalit to obtain 0 1. Since this statement is false, the part of the graph containing (0, 0) should not be shaded. Thus, the graph is correct Lesson 3-3 Graphs of Nonlinear Inequalities 147

3 To solve absolute value inequalities algebraicall, use the definition of absolute value to determine the solution set. That is, if a 0, then a a, and if a 0, then a a. Eample 4 Solve There are two cases that must be solved. In one case, 2 is negative, and in the other, 2 is positive. Case 1 ( 2) ( 2) ( 2) The solution set is { 7 11}. { 7 11} is read the set of all numbers such that is between 7 and 11. Verif this solution b graphing. First, graph 2 5. Since we are solving and 2 5, we are looking for a region in which 4. Therefore, graph 4 and graph it on the same set of aes. Identif the points of intersection of the two graphs. B inspecting the graph, we can see that the intersect at ( 7, 4) and (11, 4). Now shade the region where the graphs of the inequalities 2 5 and 4 intersect. This occurs in the region of the graph where Thus, the solution to is the set of -values such that Case 2 ( 2) ( 2) ( 7, 4) (11, 4) Nonlinear inequalities have applications to man real-world situations, including business, education, and medicine. Eample 5 PHARMACLGY Refer to the application at the beginning of the lesson. At what times during the first 4-hour period is the amount of pain reliever in the bloodstream above 300 milligrams? Since we need to know when the level of pain reliever in the bloodstream is above 300 milligrams, we can write an inequalit for 0 6 Real World A p plic atio n 148 Chapter 3 The Nature of Graphs

4 Let and 300. Graph both equations on the same set of aes using a graphing calculator. Calculating the points of intersection, we find that the two equations intersect at about (1.3, 300) and (3.1, 300). Therefore, when , the amount of pain reliever in the bloodstream is above 300 milligrams. That is, the amount eceeds 300 milligrams between about 1 hour 18 minutes and 3 hours 6 minutes after taking the medication. Weight (mg) Time (h) [0, 6] scl: 1 b [0, 500] scl: 100 C HECK FR U NDERSTANDING Communicating Mathematics Guided Practice Read and stud the lesson to answer each question. 1. Describe how knowledge of transformations can help ou graph the inequalit State the two cases considered when solving a one-variable absolute value inequalit algebraicall. 3. Write a procedure for determining which region of the graph of an inequalit should be shaded. 4. Math Journal Sketch the graphs of 3 2 and 1 on the same set of aes. Use our sketch to solve the inequalit If no solution eists, write no solution. Write a paragraph to eplain our answer. Determine whether the ordered pair is a solution for the given inequalit. Write es or no , ( 1, 3) , (0, 3) Graph each inequalit. 7. ( 1) ( 3) Solve each inequalit Manufacturing The AccuData Compan makes compact disks measuring 12 centimeters in diameter. The diameters of the disks can var no more than 50 micrometers or centimeter. a. Write an absolute value inequalit to represent the range of diameters of compact disks. b. What are the largest and smallest diameters that are allowable? Lesson 3-3 Graphs of Nonlinear Inequalities 149

5 Practice A E XERCISES Determine whether the ordered pair is a solution for the given inequalit. Write es or no , (1, 0) , (3, 8) , ( 2, 1) , (10, 63) , ( 6, 9) , (0, 0) 19. Which of the ordered pairs, (0, 0), (1, 4), (1, 1), ( 1, 0), and (1, 1), is a solution for 2? How can ou use these results to determine if the graph at the right is correct? 2 B Graph each inequalit ( 5) (0.4) ( 4) ( 1) (2 1) Sketch the graph of the inequalit C Solve each inequalit Find all values of that satisf Applications and Problem Solving Real World A p plic atio n 40. Chemistr Katie and Wes worked together on a chemistr lab. The determined the quantit of the unknown in their sample to be grams. If the actual quantit of unknown is, write their results as an absolute value inequalit. Solve for to find the range of possible values of. 41. Critical Thinking Solve Critical Thinking Find the area of the region described b and Education Amanda s teacher calculates grades using a weighted average. She counts homework as 10%, quizzes as 15%, projects as 20%, tests as 40%, and the final eam as 15% of the final grade. Going into the final, Amanda has scores of 90 for homework, 75 for quizzes, 76 for projects, and 80 for tests. What grade does Amanda need on the final eam if she wants to get an overall grade of at least an 80? 44. Critical Thinking Consider the equation ( 3) 2 4 b. Determine the value(s) of b so that the equation has a. no solution. b. one solution. c. two solutions. d. three solutions. e. four solutions. 150 Chapter 3 The Nature of Graphs

6 45. Business After opening a cookie store in the mall, Paul and Carol Mason hired an consultant to provide them with information on increasing their profit. The consultant told them that their profit P depended on the number of cookies that the sold according to the relation P() 0.005( 1200) The tpicall sell between 950 and 1000 cookies in a given da. a. Sketch a graph to model this situation. b. Eplain the significance of the shaded region. Mied Review 46. How are the graphs of f() 3 and g() 2 3 related? (Lesson 3-2) 47. Determine whether the graph of 14 is smmetric with respect to the -ais, -ais, the line, the line, or none of these. (Lesson 3-1) 48. Find the inverse of. (Lesson 2-5) Multipl b (Lesson 2-3) 50. Graph 3 5. (Lesson 1-7). 51. Criminal Justice The table shows the number of states with teen courts over a period of several ears. Make a scatter plot of the data. (Lesson 1-6) 52. Find [f g](4) and [g f](4) for f() 5 9 and g() (Lesson 1-2) 53. SAT Practice Grid-In Student A is 15 ears old. Student B is one-third older. How man ears ago was student B twice as old as student A? 8 4 Year States with Teen Courts * Source: American Probation and Parole Association. *Includes District of Columbia MID-CHAPTER QUIZ Determine whether each graph is smmetric with respect to the -ais, the -ais, the line, the line, the origin, or none of these. (Lesson 3-1) Use the graph of the given parent function to describe the graph of each related function. (Lesson 3-2) 5. f() 6. f() 3 a. 2 a. 3 3 b. 3 b. (0.5) 3 1 c c. ( 1) Sketch the graph of g() 0.5( 2) 2 3. (Lesson 3-2) 8. Graph the inequalit (Lesson 3-3) 9. Find all values of that satisf (Lesson 3-3) 10. Technolog In September of 1999, a polling organization reported that 64% of Americans were not ver or not at all concerned about the Year-2000 computer bug, with a margin of error of 3%. Write and solve an absolute value inequalit to describe the range of the possible percent of Americans who were relativel unconcerned about the Y2K bug. (Lesson 3-3) Source: The Gallup rganization Etra Practice See p. A30. Lesson 3-3 Graphs of Nonlinear Inequalities 151