Chapter 3 - Section 3.1 - Quadratic Functions and Models - 3.1 Exercises - Page 252: 51

maximum height $y= 25 ft$

Calculate the maximum of the function by substituting the values from the function into $t_{MAX}=\frac{-b}{2a}\rightarrow t_{MAX}=1.25$ which is the time the ball travels upwards. Then substitute $t=1.25$ into the function to get the maximum height.