Given 36 − 9, simplify the expression using the Difference of Squares. Wait, wait. I know what you are saying. 36 − 9 is not exactly a difficult math problem, it is 27. Yes you are correct; however, 36 − 9 is going to serve as a proof that the Difference of Squares is valid regardless of what x and y are.

36 − 9

62 − 32

This looks exactly like the Difference of Squares, x2 − y2. So substitute 6 and 3 in for x and y.