you need to find the roots of the function, h(t)
then h(t) = 0 = -16t^2 + 64t + 4
divide both sides by -4
4t^2 - 16 t - 1 = 0
use the quadratic function
\(\frac{-b+/- \sqrt{b^2-4ac} }{2a}\)
substitue a = 4, b = -16, c = -1
you will get t1 ≈ 0 and t2 ≈ 4
Answer: approx. 4 seconds.
