2 căn 3x - 3 căn 12x +5 căn 27 x =33

`2\sqrt{3x}-3\sqrt{12x}+5\sqrt{27x}=33(x>=0)`

`<=>2\sqrt{3x}-3\sqrt{2^2 .3x}+5\sqrt{3^2 .3x}=33`

`<=>2\sqrt{3x}-6\sqrt{3x}+15\sqrt{3x}=33`

`<=>\sqrt{3x}(2-6+15)=33`

`<=>11\sqrt{3x}=33`

`<=>\sqrt{3x}=3`

`<=>3x=9`

`<=>x=3(tm)`

Vậy `S={3}`