Question

Выражение 1/(х-1)(х-у)+1/(у-1)(у-х)+1/(1-х)(1-у)

Answer 1

$\frac{1}{(x-1)(x-y)}+\frac{1}{(y-1)(y-x)}+\frac{1}{(1-x)(1-y)}=$

$\frac{1}{(x-1)(x-y)}-\frac{1}{(y-1)(x-y)}+\frac{1}{(x-1)(y-1)}=$

$\frac{y-1-x+1+x-y}{(x-1)(y-1)(x-y)}=\frac{0}{(x-1)(y-1)(x-y)}}=0$

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