Word problem, help ASAP

Question

A model rocket is launched straight up, with an initial velocity of 150 m/s. The height of the rocket can be modelled by h= -5t2 + 150t, where h is the height in metres and t is the elapsed time in seconds. What is the maximum height reached by the rocket?

Answer 1

The maximum height is at the vertex of the height-vs.-time parabola, which is at

t = -150 / [2(-5)] sec = ? sec

Evaluate h(t) at this value of t to get h_max.