Step-by-step explanation:
Given that,
The quadratic equation that models the ball's height above the ground h, t seconds after it was thrown is given by :
...(1)
(a) For maximum height, put dh/dt = 0
So,
Put the value of t in equation (1).
So,
(b) When the ball reaches the ground,
h = 0
So,
So, the ball hits the ground in 7 seconds.