In two or more complete sentences, explain how to find the time it takes for a rocket following the path, h(x) = -4x 2 + 16x, to hit the ground.

Answer 1

Assuming x is time and the ground is at h=0, set h equal to zero and solve for x.

-4x² + 16x = -4x(x - 4) = 0

x = 0 or 4

But x=0 is the moment of launch from the ground, so it reaches the ground again at x = 4.