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