Also,
Slide 5.6 - 4
Notice that in the square of a sum, all of the terms are
positive. In the square of a difference, the middle term is
negative.
2
2 2
.2x y x xy y
2
2 2
.2x y x xy y
A common error when squaring a binomial is to forget the middle term of the
product. In general,
2
2 2 2 2
, not2 x y x xy y x y