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On a quiz show, 30 points are given for correct answers to Regular questions, and 60 points are given for correct answers in the Bonus round. Let R represent the number of regular questions answered correctly and B represent the number of bonus questions answered correctly. a) Write an expression that give the total number of points earned. 30R + 60B b) c) Suppose a contestant earned 900 points. Write an equation relating R, B, and the number of points earned. 30R + 60B = 900 If the contestant answered 20 regular questions correctly and earned 900 points, how many bonus questions were answered correctly? 5 Bonus Questions d) Find another possible solution to the equation in b. 3-4 The Graph of Ax + By = C Standard Form Ax + By = C • A has to be POSITIVE!!! • A and B can not be FRACTIONS or DECIMALS!!! • A and B can not BOTH be zero. • The graph of Ax + By = C, where A and B are not both 0, is a line. Finding Useful Information Standard Form : Ax + By = C -To find the x-intercept: • Substitute 0 in for y. • Solve for x • x=C/A -To find the y-intercept: • Substitute 0 in for x. • Solve for y • y=C/B -To find slope: • Subtract Ax • Divide by B • m = -A / B Example 5/24/2017 Give an equation in Standard Form for the line with y-int of – 5 and slope 3 . Identify the x-int. 4 Ax By C ←Standard Form→3 x 4 y 20 3 y x5 4 3 x y 5 4 3 4( x y 5) 4 20 x int 3 y int 5 Example 5/24/2017 Give an equation in Standard Form for the line with y-int of 7 and slope 1 . Identify the x-int. 5 Ax By C 1 y x7 5 1 x y 7 5 1 5( x y 7) 5 ←Standard Form→ x 5 y 35 x int 35 y int 7 5/24/2017 Complete the Table Standard Form Ax + By = C 5x – 10y = 30 2x + 5y = 20 6x – 7y = –42 x=–9 Slope y-intercept x-intercept –3 6 –2/5 4 10 6/7 6 –7 1/2 undefined none –9 Graphing by Intercepts To Graph by Intercepts • Find x-intercept • Plot on Graph • Find y-intercept • Plot on Graph • Draw line through the points 4x + 3y = 12 4x + 3(0) =12 4x + 3y = 12 x-int = 3 4(0) + 3y = 12 y-int = 4 5/24/2017 Graphing by Intercepts Graph the equation: 6x – 4y = 24 using its intercepts. x-int = ? 6x – 4(0) =24 x-int = 4 (4, 0) y – int = ? 6(0) – 4y =24 y-int = –6 (0, –6) Assignment • Lesson Master 3-4 • Pages 160-161 #’s 6, 8, 9,12-18, 20-22. • Study for Quiz on Sections 3-1 to 3-3!!!!!