A soccer ball is kicked from the ground with an initial upward velocity of 90 feet per second. The equation h=-16t^2 + 90t gives the height h of the ball after t seconds. What is the maximum height of the ball?

h = -16t^2 + 90t = -16(t^2 - 45/8 t) = -16((t - 45/16)^2 - (45/16)^2) = 2025/16 - 16 (t - 45/16)^2

The maximum height of the ball is 2025/16.

(The unit is missing from the question.)

Well...yah....often true....but the unit is given as feet if you look at the equation and know the initial v is 90 ft/sec......

Oh yes. you're right. I was careless.