The equation y = -16t^2 + 28t + 180 describes the height (in feet) of a ball tossed up in the air at 28 feet per second from a height of 180 feet from the ground. In how many seconds will the ball hit the ground?
When it hits the ground y = 0
So
-16t^2 + 28t + 180 = 0 divide through by -4
4t^2 - 7t - 45 = 0
Using the Quadratic Formula
t = 7 + sqrt [ 7^2 - 4 * 4 * -45 ] 7 + sqrt 769
__________________________ = _____________ ≈ 4.34 sec
2 * 4 8
