Question 39260
a) at what instant will it be back at the ground level?
Use quadratic formula to determine zeros.
*[invoke quadratic "t", -16, 96, 0]
At 6 seconds, the ball will hit the ground.
b) for what time interval is the ball more than 384ft above the ground?
{{{s(t)=96t-16t^2}}}
{{{384 < 96t - 16t^2}}}
{{{0 < -384 + 96t - 16t^2}}}
If you try to work this out, you will get an imaginery number. The ball will not reach this height. The highest the ball will go is about 144ft.