Question 306986
Set h to zero and solve for t:
h=-16t^2+18t
0=-16t^2+18t
0=-8t^2+9t
0=t(-8t+9)
.
t = {0, 9/8)
That is h (height)is zero at times:
0 secs (at the beginning)
and again at
9/8 secs (or 1.125 secs)