Graphing techniques

Question

 The height of a rocket after T seconds is given by the function H(t) =18t-3t^2.  And how many seconds the rock in attaIns maximum height?

Answer 1

H(t) = -3t² + 18t

 

The maximum height occurs at the vertex of the H vs. t parabola, which is at

 

t = -18/[2(-3)] sec = 3 sec