Упростите выражение 1/(х-1)(х-у)+1/(у-1)(у-х)+1/(1-х)(1-у)

[latex]frac{1}{(x-1)(x-y)}+frac{1}{(y-1)(y-x)}+frac{1}{(1-x)(1-y)}=[/latex] [latex]frac{1}{(x-1)(x-y)}-frac{1}{(y-1)(x-y)}+frac{1}{(x-1)(y-1)}=[/latex] [latex]frac{y-1-x+1+x-y}{(x-1)(y-1)(x-y)}=frac{0}{(x-1)(y-1)(x-y)}}=0[/latex] ................................................................................................................