Помогите решить 22 д

[latex] \frac{a^{-2}+b^{-2}}{a^{-1}+b^{-1}}\cdot( \frac{a^2+b^2}{ab})^{-1}-(a+b)^{-1}= \frac{ (\frac{1}{a})^2 +( \frac{1}{b})^2}{ \frac{1}{a}+ \frac{1}{b}}\cdot \frac{ab}{a^2+b^2}- \frac{1}{a+b}=\\\\ = \frac{ \frac{a^2+b^2}{a^2b^2}}{ \frac{a+b}{ab}}\cdot \frac{ab}{a^2+b^2}- \frac{1}{ab}= \frac{a^2+b^2}{a^2b^2}\cdot \frac{ab}{a+b}\cdot \frac{ab}{a^2+b^2} - \frac{1}{a+b}= \\\\ = \frac{1}{a+b}- \frac{1}{a+b}=0[/latex]