# Math( help please ! )

posted by
**Erin**
.

The height of a ball thrown vertically upward from a rooftop is modelled by h(t)=-5t^2=20t=50, where h(t) is the ball's height above the gorund,in meters, at time t seconds after the throw

a) determine the maximum height of the ball

b) how long does it take for the ball to reach its maximum height

c) how highis the rooftop