[tex]\displaystyle \mathtt{ \frac{1}{1- \sqrt{2} } - \frac{7}{3- \sqrt{2} }+ \sqrt{8}= \frac{1+ \sqrt{2} }{1-2}- \frac{7\left(3+ \sqrt{2}\right) }{9-2} + \sqrt{2}= }\\ \\ \mathtt{=-\left(1+ \sqrt{2}\right)- \frac{\not7\left(3+ \sqrt{2}\right) }{\not7} =-1- \sqrt{2}-\left(3+ \sqrt{2}\right)= }\\ \\ \mathtt{=-1- \sqrt{2}-3- \sqrt{2}=-1-3=-4}[/tex]
