a^2 - b^2 = (a+b)(a-b), Algebraic Formula

##### (a+b)(a-b)=a^2-b^2

Models play an important role in algebraic thinking. Here is a geometric model for *(a+b)(a-b)*, requiring almost no word. Yes, (a+b)(a-b)=a^2+ab-ab-b^2. But a picture is appealing, too. You can use all the three pieces or just the board. I do think on needs to talk about it, though.