Express the surface area S as a function of x

Question

A box is to be created from a piece of cardboard measuring 20inches×17inches by cutting out identical squares with side lengths of x from each corner and folding up the sides.

Express the volume V of the box as a function of x

V(x) = (17-2*x)*(20-2*x)*x

Express the surface area S as a function of x

S(x)=???

Answer 1

Draw and label a diagram:

bottom: (20-2x)(17-2x)

L side: x(20-2x), there are 2

S side: x(17-2x), there are 2