SOLUTION: The height of an object dropped from the top of a 64-foot building is given by h(t)=-16t^2+64. How long will it take the object to hit the ground?
The object will hit the ground when
-16*t^2 + 64 = 0 (i.e. when h(t) = 0 ).
It is the same as
16t^2 = 64
t^2 = 64/16
t^2 = 4
t = = 2.
ANSWER. In 2 seconds.