Algorithm7.1.8Factoring Out the Greatest Common Factor—Using Rectangles
Put the terms into adjacent rectangles. Think of these as labeling the areas of each rectangle.
Identify the common factor, and mark the height of the overall rectangle with it.
Mark the base of each rectangle based on each rectangle's area and height.
Since the overall rectangle's area equals its base times its height, the height is one factor, and the sum of the widths is another factor.