− v 3 u 4 + 2 v 2 u 4 − v u 4 − v 4 u 3 + 4 v 3 u 3 − 7 v 2 u 3 + 4 v u 3 + v 4 u 2 − 6 v 3 u 2 + 11 v 2 u 2 − 6 v u 2 + u 2 + 4 v 3 u − 7 v 2 u + 4 v u − u − v 3 + 2 v 2 − v {\displaystyle -v^{3}u^{4}+2v^{2}u^{4}-vu^{4}-v^{4}u^{3}+4v^{3}u^{3}-7v^{2}u^{3}+4vu^{3}+v^{4}u^{2}-6v^{3}u^{2}+11v^{2}u^{2}-6vu^{2}+u^{2}+4v^{3}u-7v^{2}u+4vu-u-v^{3}+2v^{2}-v}
