Question

А/а+7-(а-7)^2•(1/а^2-49+1/а^2-49+1/а^2-14а+49)

Answer 1

Ответ:    $\frac{7-2a}{a+7}$ .

Объяснение:

$\frac{a}{a+7}-(a-7)^2\cdot \Big (\frac{1}{a^2-49}+\frac{1}{a^2-49}+\frac{1}{a^2-14a+49}\Big )=\\\\=\frac{a}{a+7}-(a-7)^2\cdot \Big (\frac{2}{(a-7)(a+7)}+\frac{1}{(a-7)^2}\Big )=\\\\=\frac{a}{a+7}-(a-7)^2\cdot \frac{2(a-7)+(a+7)}{(a-7)^2(a+7)}=\\\\=\frac{a}{a+7}-\frac{2a-14+a+7}{a+7}=\frac{a}{a+7}-\frac{3a-7}{a+7}=\frac{a-3a+7}{a+7}=\frac{7-2a}{a+7}$