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