maximum possible volume

Question

Bobbi is going to make an open top box out of a flat sheet of metal that is 4x7 inches. He will cut equal squares out of each corner and fold up the sides. What is the maximum possible volume?

a 10.4

b .08

c 5.9

d 23.5

Answer 1

V(x) = x(4 - 2x)(7 - 2x)

Convert to vertex form and answer.