căn 12-6 căn 3 giải nhanh giúp mình vs ạ

`a)` `\sqrt{12 - 6\sqrt{3}}`

`= \sqrt{9 - 6\sqrt{3} + 3}`

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

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

`= | 3 - \sqrt{3} |`

`= 3 - \sqrt{3}` ( Do `3 > \sqrt{3}` )

`b)` `\sqrt{12}-6\sqrt{3}`

`=\sqrt{4.3}-6\sqrt{3}`

`=2\sqrt{3}-6\sqrt{3}`

`=-4\sqrt{3}`