# How do you factor p^4-q^4?

Use the relation ${p}^{2} - {q}^{2} = \left(p - q\right) \left(p + q\right)$
${p}^{4} - {q}^{4} = \left({p}^{2} - {q}^{2}\right) \left({p}^{2} + {q}^{2}\right)$
$= \left(p - q\right) \left(p + q\right) \left({p}^{2} + {q}^{2}\right)$