11-6 2 - 6-4 2

`\sqrt{11-6\sqrt2} - \sqrt{6-4\sqrt2}`

`= \sqrt{9-2.3.\sqrt2 + 2} - \sqrt{4-2.2.\sqrt2+2}`

`= \sqrt{3^2-2.3.\sqrt2 + (\sqrt2)^2} - \sqrt{2^2-2.2.\sqrt2+(\sqrt2)^2}`

`= \sqrt{ (3-\sqrt2)^2} - \sqrt{(2-\sqrt2)^2}`

`= |3-\sqrt2| - |2-\sqrt2|`

`=(3-\sqrt2) - (2-\sqrt2)`(do `3 = \sqrt9  > \sqrt2` ; `2 = \sqrt4 > \sqrt2`)

`= 3 - \sqrt2 - 2 + \sqrt2`

`= 1`