`10)` `(\sqrt{2}-\sqrt{6}).\sqrt{2+\sqrt{3}}`
`=\sqrt{2}(1-\sqrt{3}).\sqrt{2+\sqrt{3}}`
`=(1-\sqrt{3}).\sqrt{2(2+\sqrt{3})}`
`=(1-\sqrt{3}).\sqrt{4+2\sqrt{3}}`
`=(1-\sqrt{3}).\sqrt{3+2\sqrt{3.1}+1}`
`=(1-\sqrt{3}).\sqrt{(\sqrt{3}+1)^2}`
`=(1-\sqrt{3}).|\sqrt{3}+1|`
`=(1-\sqrt{3})(1+\sqrt{3})` (do `\sqrt{3}+1>0)`
`=1-3`
`=-2`
`11)` `frac{2+\sqrt{2}}{1+\sqrt{2}}-frac{2-\sqrt{2}}{1-\sqrt{2}}`
`=frac{\sqrt{2}(\sqrt{2}+1)}{1+\sqrt{2}}-frac{\sqrt{2}(\sqrt{2}-1)}{-(\sqrt{2}-1)}`
`=\sqrt{2}+\sqrt{2}`
`=2\sqrt{2}`
