How to Factor the Difference of Two Perfect Squares

If two terms in a binomial are perfect squares separated by subtraction, then you can factor them. To factor the difference of two perfect squares, remember this rule. If subtraction separates two squared terms, then the sum and the difference of the two square roots factors the binomial. For example, a2 – b2 = (a + b)(ab)

Factor 9x2 – 16

  1. Find the square roots of the two terms that are perfect squares.

    The square roots of 9x2 and 16 are 3x and 4, respectively.

  2. Write the factorization as the sum and difference of the square roots.

    The sum of the roots is 3x + 4 and the difference between the roots is 3x – 4.

    So, 9x2 – 16 = (3x + 4) (3x – 4).

Factor x2 – 3

  1. Find the square roots of the two terms that are perfect squares.

    The square root of x2 is x, and you can write the square root of 3 as the following:

    image0.png
  2. Write the factorization as the sum and difference of the square roots.

    image1.png

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