Question 989069
h=-16t^2+64t
h=48
Therefore, -16t^2+64t=48,
16t^2-64t+48=0
dividing by 16
t^2-4t+3=0
(t-3)(t-1)=0
and t=1 and 3 seconds it will be 48 feet above the ground.
It will hit the ground when -16t^2+64t=0, or t=4 seconds.
{{{graph(300,200,-5,5,-5,75,-16x^2+64x)}}}