Помогите плиз, срочно!!!!!!!

( $( \frac{1}{a+ \sqrt{2} } - \frac{ a^{2}+4 }{(a+ \sqrt{2})( a^{2}- \sqrt{2}a+2) } }): ( \frac{ a^{2}- \sqrt{2}a+2 }{2a}) ^{-1}= \frac{ a^{2}- \sqrt{2}a+2- a^{2}-4 }{(a+ \sqrt{2})( a^{2}- \sqrt{2}a+2) }: [tex] \frac{2a}{ a^{2}- \sqrt{2}a+2 }= \frac{- \sqrt{2}a-2 }{(a+ \sqrt{2})( a^{2} - \sqrt{2}a+2) }* \frac{ a^{2}- \sqrt{2}a+2 }{2a}= \frac{- \sqrt{2}(a+ \sqrt{2}) }{(a+ \sqrt{2})2a }=- \frac{ \sqrt{2} }{2a}$