− 2 v u 4 + u 4 − 4 v 2 u 3 + 8 v u 3 − 4 u 3 + 6 v 2 u 2 − 13 v u 2 + 6 u 2 − 4 v 2 u + 8 v u − 4 u + v 2 − 2 v {\displaystyle -2vu^{4}+u^{4}-4v^{2}u^{3}+8vu^{3}-4u^{3}+6v^{2}u^{2}-13vu^{2}+6u^{2}-4v^{2}u+8vu-4u+v^{2}-2v}
