− v 2 u 4 + v u 4 + 4 v 2 u 3 − 5 v u 3 + u 3 − 4 v 2 u 2 + 7 v u 2 − 4 u 2 + v 2 u − 5 v u + 4 u + v − 1 {\displaystyle -v^{2}u^{4}+vu^{4}+4v^{2}u^{3}-5vu^{3}+u^{3}-4v^{2}u^{2}+7vu^{2}-4u^{2}+v^{2}u-5vu+4u+v-1}
