Question 387214
h(t) = -9.8t^2 – 10t + 310
Set h(t) to zero (since when height = 0, it'll hit the ground):
0 = -9.8t^2 – 10t + 310
since we can't factor, we apply the "quadratic formula".  Doing so yields:
x = {-6.16, 5.14}
We can toss out the negative solution leaving:
x = 5.14 seconds
.
Details of quadratic follows:
*[invoke quadratic "x", -9.8, -10, 310 ]