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