− v 3 u 4 + v 2 u 4 − v 4 u 3 + 4 v 3 u 3 − 4 v 2 u 3 + 2 v u 3 + v 4 u 2 − 4 v 3 u 2 + 7 v 2 u 2 − 4 v u 2 + u 2 + 2 v 3 u − 4 v 2 u + 4 v u − u + v 2 − v {\displaystyle -v^{3}u^{4}+v^{2}u^{4}-v^{4}u^{3}+4v^{3}u^{3}-4v^{2}u^{3}+2vu^{3}+v^{4}u^{2}-4v^{3}u^{2}+7v^{2}u^{2}-4vu^{2}+u^{2}+2v^{3}u-4v^{2}u+4vu-u+v^{2}-v}
