Question: Find the maximum y value of the graph between 0 ≤ x ≤ 3

Equation:

f(x) = x(8-2x)(6-2x)

Answer:

24.26

How would you find the maximum y value of this graph? Is it not like a parabola so when I tried finding the midpoint and then using the quadratic formula it didn't give me the highest value. Please explain the process and show your work. Thanks.