a) ( căn 12 -2căn 3 ).căn 3- căn 5 b)2 căn 16/3 - 3 căn 1/27 -3/căn 3 c) căn (-3) ² +3/ căn 2+ căn 1/2 -2căn 18

`a) ( \sqrt{12} - 2 \sqrt{3} ). \sqrt{3} - \sqrt{5}`

`= 0 . \sqrt{3} - \sqrt{5}`

`= - \sqrt{5}`

`b) 2 \sqrt{\frac{16}{3}} - 3 \sqrt{frac{1}{27}} - 3 \sqrt{3}`

`= \frac{8 \sqrt{3}}{3} - \frac{\sqrt{3}}{3} - \frac{9 \sqrt{3}}{3}`

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

`c) \sqrt{( -3 )²} + \frac{3}{\sqrt{2}} + \sqrt{1/2} - 2 \sqrt{18}`

`= | -3 | + \frac{3 \sqrt{2}}{2} + \frac{\sqrt{2}}{2} - \frac{12 \sqrt{2}}{2}`

`= 3 - 4 \sqrt{2}`