How can you tell if an expression is a perfect square trinomial? Explain.

Step-by-step explanation:

A perfect square trinomial is the square of a binomial.

One of the special products and factors formulas that you should know is

(a + b) ^2 = a^2 + 2ab + b^2; another is (a - b) ^2 = a^2 - 2ab + b^2.

So, if you are given a trinomial and can use either of the above identities to rewrite it as the square of a binomial, you've got it.