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Đáp án:

 `c)(sqrt(3)-3)/(1-sqrt(3))`
`=- (sqrt(3)(1-sqrt(3) )) / (1-sqrt(3))`

`=-sqrt3`
`d)(5 +2sqrt5)/sqrt5 + (3+sqrt3)/sqrt3`
`=(sqrt5(sqrt(5)+2)) / sqrt5 +(sqrt3(sqrt(3)+1))/sqrt3`

`=sqrt(5)+2 + sqrt(3)+1`

`=sqrt5+sqrt3 +3`