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?

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.

Answer: 2.5 seconds