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,
![(d(h))/(dt)=(d)/(dt)(-16t^2+108t+28)=0\\\\-32t+108=0\\\\t=(108)/(32)=3.37\ s](https://img.qammunity.org/2022/formulas/mathematics/college/jrnaa68sxd3536nqp78ae5bl7fiowpurr6.png)
Put the value of t in equation (1).
So,
![h=-16(3.37)^2+108(3.37)+28\\\\h=210.24\ ft](https://img.qammunity.org/2022/formulas/mathematics/college/j2xcnh8el2jbxsy9qdjle70gqknlqysbdi.png)
(b) When the ball reaches the ground,
h = 0
So,
![-16t^2+108t+28=0\\\\t=7\ s](https://img.qammunity.org/2022/formulas/mathematics/college/iqapvw932mk73c96of8gqwoyllhfmwopdv.png)
So, the ball hits the ground in 7 seconds.