u 4 v 4 − u 4 v 3 − u 3 v 4 + 4 u 3 v 3 − 3 u 3 v 2 − 3 u 2 v 3 + 7 u 2 v 2 − 3 u 2 v − 3 u v 2 + 4 u v − u − v + 1 u 2 v 2 {\displaystyle {\frac {u^{4}v^{4}-u^{4}v^{3}-u^{3}v^{4}+4u^{3}v^{3}-3u^{3}v^{2}-3u^{2}v^{3}+7u^{2}v^{2}-3u^{2}v-3uv^{2}+4uv-u-v+1}{u^{2}v^{2}}}}
