Here's the way I like to think through these factoring problems involving the difference of two squares. First, make sure dealing with a perfect square minus a perfect square. In this case we are.
So this binomial will factor as the product of two binomials.
The first binomial will have a + in the middle and the second binomial will have a - in the middle. In the first position, we will have the factors of x² that are the same so x time x. In the second position will be the factors of 16 that are the same, 12 times 12.
(x + 4)(x - 4) is your answer, a factored version of x² - 16.
