Summary: Factoring Special Cases

Key Concepts

Perfect Square Trinomials A perfect square trinomial can be written as the square of a binomial:

${a}^{2}+2ab+{b}^{2}={\left(a+b\right)}^{2}$

${a}^{2}-2ab+{b}^{2}={\left(a-b\right)}^{2}$

How to factor a perfect square trinomial

Confirm that the first and last term are perfect squares.
Confirm that the middle term is twice the product of $ab$ .
Write the factored form as ${\left(a+b\right)}^{2}$ or ${\left(a-b\right)}^{2}$ .

Differences of Squares A difference of squares can be rewritten as two factors containing the same terms but opposite signs.

${a}^{2}-{b}^{2}=\left(a+b\right)\left(a-b\right)$

The Sum of Cubes A binomial in the form $a^{3}+b^{3}$ can be factored as $\left(a+b\right)\left(a^{2}–ab+b^{2}\right)$ .

The Difference of Cubes A binomial in the form $a^{3}–b^{3}$ can be factored as $\left(a-b\right)\left(a^{2}+ab+b^{2}\right)$ .