− v 2 u 4 + 2 v u 4 − u 4 + 3 v 2 u 3 − 6 v u 3 + 3 u 3 − 4 v 2 u 2 + 7 v u 2 − 4 u 2 + 3 v 2 u − 6 v u + 3 u − v 2 + 2 v − 1 {\displaystyle -v^{2}u^{4}+2vu^{4}-u^{4}+3v^{2}u^{3}-6vu^{3}+3u^{3}-4v^{2}u^{2}+7vu^{2}-4u^{2}+3v^{2}u-6vu+3u-v^{2}+2v-1}
