$$\frac{pq-pr}{r^{2}-1}\div\frac{q^{2}-r^{2}}{r^{2}+r}$$
$\frac{pr}{\left(r-1\right)\left(q+r\right)}$
$r\neq 0\text{ and }|r|\neq 1\text{ and }|q|\neq |r|$
$\frac{pr}{\left(r-1\right)\left(q+r\right)}$
$r\neq 0\text{ and }|r|\neq 1\text{ and }|q|\neq |r|$