Drag the green dot to vary the rectangle. [br]Drag the red dot to find out which is bigger.

Which is bigger, the rectangle or the square?

Introduce the identity, difference of two squares, through a problem about comparing areas. See the making of this file in YouTube -> [url=http://youtu.be/v809gcQTfD4 ]http://youtu.be/v809gcQTfD4 [/url]