Question

\frac{{xy}}{{x - y}} ∙\left( {\frac{1}{x} + \frac{1}{y}} \right) − \frac{{x + y}}{{x - y}}

Answer 1

$\displaystyle\frac{{xy}}{{x - y}} \cdot\left( {\frac{1}{x} + \frac{1}{y}} \right) -\frac{{x + y}}{{x - y}}= \frac{xy}{x-y}\cdot \frac{x+y}{xy} - \frac{x+y}{x-y} =\\ \\ \\ = \frac{x+y}{x-y}- \frac{x+y}{x-y} =0$