236 CHAPTER 2 Graphs and Functions Determine the largest open intervals of the domain over which each function is (a) increasing, (b) decreasing, and (c) constant. See Example 9. 87. x y (0, –2) (–2, –4) 0 2 –2 –4 2 88. 89. 90. 91. 92. 0 4 8 12 Noon 16 20 24 700 900 1100 1300 1500 1700 1900 2100 2300 2500 x Hours Electricity Use Electricity (in megawatts) Data from Sacramento Municipal Utility District. y (Modeling) Solve each problem. See Example 10. 0 1 2 3 4 5 6 7 64 128 192 256 t y Time (in seconds) Height (in feet) Height of a Thrown Ball y = h(t) 94. Height of a Ball A ball is thrown straight up into the air. The function y = h1t2 in the graph gives the height of the ball (in feet) at t seconds. (Note: The graph does not show the path of the ball. The ball is rising straight up and then falling straight down.) (a) What is the height of the ball at 2 sec? (b) When will the height be 192 ft? (c) During what time intervals is the ball going up? down? (d) How high does the ball go? When does the ball reach its maximum height? (e) After how many seconds does the ball hit the ground? (–1, 3) (–3, 1) 0 2 –1 –2 1 –3 3 x y x y (–2, 4) (2, –4) 0 2 –2 –4 4 x y (–3, –1) (3, 1) 0 3 –3 –1 1 x y (–1, –3) (1, –3) (0, –2) 0 2 –2 x y (–2, 0) (2, 0) (0, –4) 0 93. Electricity Usage The graph shows the daily megawatts of electricity used on a record-breaking summer day in Sacramento, California. (a) Is this the graph of a function? (b) What is the domain? (c) Estimate the number of megawatts used at 8 a.m. (d) At what time was the most electricity used? the least electricity? (e) Call this function ƒ. What is ƒ1122? Interpret this answer. (f) During what time intervals is usage increasing? decreasing?
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