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