`2/(2+sqrt{3})`

`= (2(2-sqrt{3}))/((2-sqrt{3})(2+sqrt{3}))`

`= (2(2-sqrt{3}))/(4-3)`

`= (2(2-sqrt{3}))/1`

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

`= 4-2sqrt{3}`

`-------------`

`***` Sử dụng phương thức nhân liên hợp

`A/(B+sqrt{C}) = (A(B-sqrt{C}))/((B-sqrt{C})(B+sqrt{C}))`

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