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