The height h (in feet) above the water of a cliff diver is modeled by h=−16t2+8t+80 , where t is the time (in seconds). How long is the diver in the air?
Accepted Solution
A:
The height above the water is h = -16t² + 8t + 80.
When the diver is above the water, h > 0. Solve the equation -16t² + 8t + 80 = 0
Divide through by -8. 2t² - t - 10 = 0
Factorize. (2t - 5)(t + 2 ) = 0 t = 2.5 or t = 2 Reject negative time, so that t = 2.5 seconds. Therefore the time the diver is above the water is 2.5 sec.