Question

ПОМОГИТЕ ДАМ 30 БАЛЛОВ

Answer 1

Просто приводим к одному знаменателю
$frac{1}{(x-y)(y-z)} - frac{1}{(y-z)(x-z)} - frac{1}{(z-x)(y-x)} = \ = frac{1}{(x-y)(y-z)} - frac{1}{(y-z)(x-z)} - frac{1}{(x-z)(x-y)} = \ =frac{x-z}{(x-y)(y-z)(x-z)} - frac{x-y}{(y-z)(x-z)(x-y)} - frac{y-z}{(x-z)(x-y)(y-z)} = \ =frac{x-z-x+y-y+z}{(x-y)(y-z)(x-z)} =0$

$frac{1}{(a-b)(a-c)} + frac{1}{(b-a)(b-c)} + frac{1}{(c-a)(c-b)} = \ = frac{1}{(a-b)(a-c)} - frac{1}{(a-b)(b-c)} + frac{1}{(a-c)(b-c)} =\ = frac{b-c}{(a-b)(a-c)(b-c)} - frac{a-c}{(a-b)(b-c)(a-c)} + frac{a-b}{(a-c)(b-c)(a-b)}= \ =frac{b-c-a+c+a-b}{(a-b)(a-c)(b-c)} =0$