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] ................................................................................................................