115. \(\frac{2a+2b}{b}\cdot\left(\frac{1}{a-b}-\frac{1}{a+b}\right)\)

\(\frac{2a+2b}{b}\cdot\left(\frac{1}{a-b}-\frac{1}{a+b}\right)=\frac{2(a+b)}{b}\cdot\frac{(a+b)-(a-b)}{(a-b)(a+b)}=\frac{2(a+b)}{b}\cdot\frac{2b}{(a-b)(a+b)}=\frac{4}{a-b}\).

Ответ: \(\frac{4}{a-b}\).