$$G ^ { 2 } = ( 2 p - q ) ( 2 q - p )$$
$G=\sqrt{\left(2p-q\right)\left(2q-p\right)}$
$G=-\sqrt{\left(2p-q\right)\left(2q-p\right)}\text{, }p\geq \frac{-3|q|+5q}{4}\text{ and }p\leq \frac{3|q|+5q}{4}$
$p=\frac{\sqrt{9q^{2}-8G^{2}}+5q}{4}$
$p=\frac{-\sqrt{9q^{2}-8G^{2}}+5q}{4}\text{, }|G|\leq \frac{3\sqrt{2}|q|}{4}$
