Question

(X+y)(x-y)

Answer 1

http://www.purplemath.com/modules/specfact.htm

Answer 2

This (x+y)(x-y) constitutes a "special product. You might want to make a list of such special products and factors:

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

Try applying this formula to the problem at hand.

Answer 3

you can also set up this rectangle