Posted by Jim on Wednesday, March 7, 2012 at 12:33am.
From a rectangular piece of cardboard having dimensions a × b, where a = 40 inches and b = 70 inches, an open box is to be made by cutting out an identical square of area x2 from each corner and turning up the sides (see the figure). Express the volume V of the box in terms of x. (Factor your answer completely.)

Precalculus  Steve, Wednesday, March 7, 2012 at 11:48am
after turning up the corners, the bottom now measures
(a2x)(b2x)
The depth of the box is the size of the tabs folded up, or x
V = (a2x)(b2x)(x)
= x(402x)(702x)
= 4x(20x)(35x)