Question

What is the value of 't'
in h(t)=-16t^3+100t if h=72

Answer 1

You want to solve
-16t^3+100t = 72
or, equivalently,
4t^3 - 25t - 72 = 0
It's not immediately clear what the roots are, but a little tinkering shows that
h(2) = 0
So, now you just have to solve
h(t) = -(t-2)(4t^2+8t-9) = 0
and you can just crank it out using the Quadratic Formula.

Answer 2

-16t^3+100t