Tính: $\sqrt{6,5+\sqrt{12}}$ + $\sqrt{6,5-\sqrt{12}}$ + 2$\sqrt{6}$

`\sqrt[6,5 + \sqrt[12]] + \sqrt[6,5 - \sqrt[12]] + 2\sqrt[6]`

`= 1/(\sqrt[2]) ( \sqrt[2] . \sqrt[6,5 + \sqrt[12]] +\sqrt[2] .  \sqrt[6,5 - \sqrt[12]] + \sqrt[2] . 2\sqrt[6] )`

`= 1/(\sqrt[2])(\sqrt[13 + 2\sqrt[12]] + \sqrt[13 - 2\sqrt[12]] + 2\sqrt[12] )`

`= 1/(\sqrt[2])(\sqrt[12 + 2\sqrt[12] + 1] + \sqrt[12 - 2\sqrt[12] + 1] + 2\sqrt[12] )`

`= 1/(\sqrt[2])(\sqrt[(\sqrt[12] + 1)^2] + \sqrt[(\sqrt[12] - 1)^2] + 2\sqrt[12] )`

`= 1/(\sqrt[2])(\sqrt[12] + 1 + \sqrt[12] - 1 + 2\sqrt[12] )`

`= 1/(\sqrt[2]) . 4\sqrt[12]`

`= 4\sqrt[6`]