$\text{Bài 3: Tìm x}$
$\text{a, 3x-2,1=}$ `\sqrt{9/25}`
$\text{3x-2,1=}$ `3/5`
$\text{3x-2,1=}$ `0,6`
$\text{3x=}$ `0,6+2,1`
$\text{3x=}$ `2,7`
$\text{x=}$ `2,7:3`
$\text{x=}$ `0,9`
$\text{Vậy x= 0,9}$
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$\text{b, 2x-}$ `\sqrt{4/9}` $\text{= 0,5 -}$ `3/4`
$\text{2x-}$ `2/3` $\equiv$ `1/2` $-$ `3/4`
$\text{2x-}$ `2/3` $\equiv$ `2/4` $-$ `3/4`
$\text{2x-}$ `2/3` $\equiv$ `-1/4`
$\text{2x}$ $\equiv$ `-1/4` $+$ `2/3`
$\text{2x}$ $\equiv$ `-3/12` $+$ `8/12`
$\text{2x}$ $\equiv$ `5/12`
$\text{x}$ $\equiv$ `5/12` $:$ `2`
$\text{x}$ $\equiv$ `5/12` $.$ `1/2`
$\text{x}$ $\equiv$ `5/24`
$\text{Vậy}$ $\text{x}$ $\equiv$ `5/24`
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$\text{c,}$ `\sqrt{x}` $-$ $\text{3 = }$ `1/2` $\text{(x}$ $\ge$ $\text{0)}$
`\sqrt{x}` $\text{=}$ `1/2` $+$ $\text{3}$
`\sqrt{x}` $\text{=}$ `1/2` $+$ `6/2`
`\sqrt{x}` $\text{=}$ `7/2`
$\Rightarrow$ `\sqrt{x}` $\text{=}$ `49/4` $\text{Thỏa mãn điều kiện x}$ $\ge$ $\text{0}$
$\text{Vậy x = }$ `49/4`
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$\text{d, 2}$$x^2$ $\text{- 5 = }$ `1/4`
$\text{2}$$x^2$ $\text{=}$ `1/4` $+$ $\text{5}$
$\text{2}$$x^2$ $\text{=}$ `1/4` $+$ `20/4`
$\text{2}$$x^2$ $\text{=}$ `21/4`
$x^2$ $\text{=}$ `21/4` $:$ $\text{2}$
$x^2$ $\text{=}$ `21/4` $.$ `1/2`
$x^2$ $\text{=}$ `21/8`
$\Rightarrow$ $\text{x=}$ $\pm$ $\sqrt{21}$`/`$\sqrt{8}$
$\text{Vậy x=}$ $\pm$ $\sqrt{21}$`/`$\sqrt{8}$
