algebra 2 graphing parabola

Question

A ball is thrown directly upward from a height of 4 ft with an initial velocity of 20 ft/sec. The function s(t)=−16t2+20t+4 gives the height of the​ ball, in​ feet, t seconds after it has been thrown. Determine the time at which the ball reaches its maximum height and find the maximum height.

Answer 1

Either of two solutions:

Convert to vertex form

Or

Maximum is at x = -20 / 2(-16)