If a football player passes a football from 4 feet off the ground with an initial velocity of 36 feet per second, how long will it take the football to hit the ground? Use the equation h = - 16t2 + 36t + 4.

0 = - 16t² + 36t + 4

0 = - 8t² + 18t + 2 ← Complete the square to solve

-8 (t² - 9t/2) = - 2

8 (t² - 9t/4 + 81/64) = 2 + 81/8

8 (t - 9/8) ² = 97/8

(t - 9/8) ² = 97/64

t - (t = 0)

(h = 0) at:

t = (9 + √97) / 8 ≅ 2.356 seconds