# How do you factor 25z^4 - 5z^2 - 12?

Substitute $x = 5 {z}^{2}$ to simplify the expression to become
${x}^{2} - x - 12$
$= \left(x - 4\right) \left(x + 3\right)$
$\left(5 {z}^{2} - 4\right) \left(5 {z}^{2} + 3\right)$