The Difference of Squares 

Some quadratic binomials are the difference of two perfect squares.  When this is the case, they can be factored as a difference times a sum, and the following formula applies:

a² – b² = (a – b)(a + b)

Example 7:  Factor 9x² – 4

Solution:  9x² = 3x ^. 3x and 4 = 2 ^. 2, so this binomial is the difference of two squares.  It factors as:

9x² – 4 = (3x – 2)(3x + 2)

toc | return to top | previous page | next page