A-18 ANSWERS 87. = − y 2 89. = − x 3 91. a) D(4, 2) b) = A 10 square units 93. (7, 2) or −( 1, 2) 95. −3 97. 3 99. a) s C 80 40 120 160 200 Cost ($) C 5 40 1 0.30s (200, 100) (0, 40) (500, 190) 100 200 300 400 500 Square Feet b) $130 c) 100 square feet 101. a) x C 400 200 600 800 1400 1200 1000 Cost ($) (20, 575) C 5 75 1 25x (0, 75) (50, 1325) 10 20 30 36 40 50 Number of Months b) $825 c) 36 months 103. a) 2 b) = + y x2 9 c) 15 defects d) 4 workers 105. a) 4.5 − b) y x 4.5 124 = − + c) 110.5 million landlines d) 2027 107. a) Solve the equations for y to put them in slopeintercept form. Then compare the slopes and y-intercepts. If the slopes are equal but the y-intercepts are different, then the lines are parallel. b) The lines are parallel. SECTION 6.7, PAGE 361 1. System 3. Inconsistent 5. Dependent 7. One 9. Infinite 11. (2, 6) 13. (0, 3) 15. (2, 1) 17. −( 2, 3) 19. No solution; inconsistent system 21. An infinite number of solutions; dependent system 23. (1, 10) 25. (1, 1) − 27. No solution; inconsistent system 29. (3, 1) 31. (3, 5) 33. An infinite number of solutions; dependent system 35. (3, 1) 37. ( 4, 5) − 39. −( 2, 2) 41. (2, 3) − 43. An infinite number of solutions; dependent system 45. No solution; inconsistent system 47. ( ) , 28 19 34 19 49. a) Cost for Ugly Truck Rentals: = + C x 0.79 30 Cost for Discount Rentals: = + C x 0.85 24 51. x y 2 2 24 22 24 4 4 (0, 0) (3, 1) (23, 21) y 5 x 1– 3 22 53. x y 2 2 22 24 4 4 (0, 2) (2, 0) x 1 y 5 2 22 24 55. (1, 0) (0, 1) x 1 y 5 1 4 24 22 4 22 24 x y 2 2 57. x 2 2 22 4 6 4 (0, 6) (3, 0) 2x 1 y 5 6 22 24 y 59. (0, 3) (6, 0) 4 2 2 4 6 22 22 x 1 2y 5 6 x y 61. 2 2 24 22 24 2x 5 24y 2 8 (0, 22) (24, 0) x y 63. 2 65. 7 3 67. 0 69. Undefined 71. (0, 2) (1, 3) 4 2 2 4 24 22 24 y 5 x 1 2 x y 22 73. (0, 3) (1, 1) 2 4 22 24 y 522x 1 3 x y 4 2 22 24 75. (0, 1) (2, 0) 4 2 2 24 22 22 24 y 52 x 1 1 1 2 x y 4 77. x y 22 2 22 4 3x 2 2y 1 6 5 0 (22, 0) (0, 3) 79. = − + y x 3 4 3 81. = + y x3 2 83. x y 2 (3, 2) 2 4 22 24 4 x 5 3 (3, 22) 22 24 Slope is undefined 85. x y 2 (22, 3) (2, 3) 2 4 22 24 4 y 5 3 22 24 Slope is 0.
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