− v u 4 + u 4 − 2 v 2 u 3 + 4 v u 3 − 2 u 3 + 3 v 2 u 2 − 5 v u 2 + 3 u 2 − 2 v 2 u + 4 v u − 2 u + v 2 − v {\displaystyle -vu^{4}+u^{4}-2v^{2}u^{3}+4vu^{3}-2u^{3}+3v^{2}u^{2}-5vu^{2}+3u^{2}-2v^{2}u+4vu-2u+v^{2}-v}
