Read the diagram in two compatible ways. The outside dimensions give one expression for the area of the whole square, while multiplying the side lengths of all four regions gives a sum for that same area. Count repeated congruent regions separately before combining like terms; equating whole and parts then produces the identity.
Inside Gozunta
Turn the preview into practice.
More than a preview
Gozunta lets you study this problem—and more than 10,000 others.
Create targeted learning sessions, use hints, check your answer, read the walkthrough, watch the video, print the work, and track your progress.