1. Greatest Common Factor (GCF)
$ax \pm ay = a(x \pm y)$
2. Difference of Squares
$a^2 - b^2 = (a - b)(a + b)$
3. Perfect Square Trinomial
$a^2 \pm 2ab + b^2 = (a \pm b)^2$
4. Partial vs. Full Canceling
Cancel matching factors, but keep remaining terms in final answer!