how do you foil this?

ab and ab are put together creating "a" squared and "b "squared Then you multiply (8*ab) and (-9*ab) which gives you +8ab and -9ab -9*8 which gives you a squared*b squared - 1 ab-72 or a squared b squared - 1ab-72. Sorry, but I have no idea how to do square numbers on the computer.

Nancy n.