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