− ( v 2 − v + 1 ) ( u v 2 − u v + u + v − 1 ) ( u v 2 − u v − v 2 + v − 1 ) u v 3 {\displaystyle -{\frac {\left(v^{2}-v+1\right)\left(uv^{2}-uv+u+v-1\right)\left(uv^{2}-uv-v^{2}+v-1\right)}{uv^{3}}}}
