How do we Factor the difference of squares?

This expression is called a difference of two squares. 

The factors of          are and     

Example 1:

Factor:   x2 - 9Both x2 and 9 are perfect squares.  Since subtraction is occurring between these squares, this expression is the difference of two squares. What times itself will give x2 ?  The answer is x. What times itself will give 9 ?  The answer is 3. These answers could also be negative values, but positive values will make our work easier. The factors are (x + 3) and (x - 3). Answer:  (x + 3) (x - 3)  or   (x - 3) (x + 3)   (order is not important)

Here is a video to help you understand better....