Question 387697
h(t) = -9.8t2 – 10t + 350
Set h(t) to 0 and solve for t:

0 = -9.8t2 – 10t + 350

0 = -4.9t2 – 5t + 175
t = {-6.51, 5.49}
Only the positive answer makes sense:
t = 5.49 seconds
.
details of quadratic:
*[invoke quadratic "t", -4.9, -5, 175 ]