Question 949108
we are given
h=-16t^2+32t+48
when object hits the ground, h = 0, therefore
0 = -16t^2+32t+48
divide both sides of = by 16
-t^2 +2t + 3 = 0
factor equation
(-t+3)(t+1) = 0
then we have t = 3 and t = -1
we want the positive value for t 
the object will hit the ground in 3 seconds