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