It will reach 80 feet for the second time after 5 seconds.
We set the equation equal to 80 feet:
80= -16t² + 96t
When solving quadratics, we want it equal to 0, so we subtract 80 from both sides:
80-80= -16t² + 96t - 80
0= -16t² + 96t - 80
We use the quadratic formula to solve: