Избавься от иррациональности и запиши ответы

1. \(\dfrac{1}{\sqrt{7}} = \) [ ];
2. \(\dfrac{2}{3\sqrt{2}} = \) [ ];
3. \(\dfrac{3}{\sqrt{x+y}} = \) [ ];
4. \(\dfrac{1}{\sqrt{a-b}} = \) [ ];
5. \(\dfrac{x+2}{\sqrt{x^2-4}} = \) [ ].