`a^2-b^2 = (a-b)(a+b)` `(a+b)^2 = a^2 + 2ab +b^2` `(a - b)^2 = a^2 - 2ab +b^2` `(a + b)^3 = a^3+3a^2b+3ab^2+b^3` `(a - b)^3 = a^3-3a^2b+3ab^2-b^3`