21.5 Factoring perfect square trinomials: $(a + b)^2 = a^2 + 2ab + b^2$ or $(a  b)^2 = a^2  2ab + b^2$
Factoring perfect square trinomials: $(a + b)^2 = a^2 + 2ab + b^2$ or $(a  b)^2 = a^2  2ab + b^2$
Some polynomials have common patterns, which can be factorized faster if you can recognize them. Perfect square trinomial is one of these cases.
Lessons

1.
Factor the perfect squares

2.
Find the square of a binomial: