Question 452048
When a ball is thrown, its height in feet h  after t seconds is given by the equation 

h=vt-16t^2 -> -16t^2 + vt - h = 0

Given: v=19 fps
Find all values of t for which h=5 ft.

We need to solve the quadratic equation for t:
-16t^2 + 19t - 5 = 0
t = (-19 +- sqrt(19^2 -4(16)(5)))/-32
This gives t = 0.39, 0.79
So the two times are t = 0.39 s and 0.79 s.
The graph of the ball's trajectory is below:
{{{graph(300,300,-3,3,-6,6,-16x^2+19x)}}}