i need help with math

Question

A rock is thrown from the side of a ledge. The height (in feet), x seconds after the toss is modeled by:

  2  3  72

What is the maximum height that the rock reached?

Answer 1

72 feet = max height, reached in 3 seconds

the parabola is in vertex form a(x-h)+k where (h,k) is the vertex with k=max height in h seconds

to be realistic though, the coefficient should be -16, not -2, to reflect the force of gravity