# How do you factor completely 25x^2– 144?

$\left(5 x + 12\right) \left(5 x - 12\right)$
$25 {x}^{2} - 144$ is a difference of squares,
${a}^{2} - {b}^{2}$, where $a = 5 x$ and $b = 12$,
${a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$.