Answer:
5 seconds
Explanation:
When the ball returns to its original height, it will be 96 ft from the ground. That means we want to solve for t ...
h(t) = 96
96 +80t -16t^2 = 96
16t(5 -t) = 0 . . . . subtract 96 and factor
This equation is true for t=0 and for t=5.
After 5 seconds, the ball will pass the top of the building on the way down.