`a)` `\sqrt{2/3}=\sqrt{{2.3}/{3^2}}=1/3 \sqrt{6}`
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`b)` `\sqrt{{x^2}/2}=\sqrt{{2x^2}/{2^2}}=|x|/2\sqrt{2}`
`={x\sqrt{2}}/2` (vì `|x|=x` với `x>0)`
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`c)` `\sqrt{{11}/{x^3}}=\sqrt{{11x}/{x^4}}=\sqrt{{11x}/{(x^2)^2}`
`=\sqrt{11x}/|x^2|=\sqrt{11x}/{x^2}`
(Vì `|x^2|=x^2>0` với mọi `x>0)`
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`d)` `\sqrt{x-x/5}=\sqrt{{5x-x}/5}`
`=\sqrt{{4x}/5}=\sqrt{{4x.5}/{5^2}}`
`=\sqrt{{2^2}/{5^2} .5x}=2/5\sqrt{5x}` `(x>0)`
