**Recognizing Differences of Squares**

The following polynomials are differences of squares:

X^{2} – 9, 4t^{2} – 49, a^{2} – 25b

Difference Of Squares

A^{2} – B^{2} = (A + B) (A – B)

Thus,

X^{2} – 9 = (x + 3) (x – 3).

To use this formula, we must be able to recognize when it applies. A **difference ****of squares **is an expression like the following:

A^{2} – B^{2}.

How can we recognize such expressions? Look at A^{2} – B^{2 } In order for a binomial to be a difference of squares:

**a) **There must be two expressions, both squares, such as

4x^{2} , 9, 25t^{4},1, x^{6}, 49y^{8}

**b) **The terms must have different signs.