Câu 14: (2 điểm). Tìm x biết: a) x + $\frac{2}{5}$ = $\frac{7}{10}$ b) $\frac{x}{-26}$ = $\frac{7}{2}$ c) |x - $\frac{1}{2}$| - $\frac{1}{3}$ = $\frac{5}{6}$

`a . ` `x+2/5=7/10`

`=>` `x=7/10-2/5`

`=>` `x=3/10`

Vậy `x=3/10`

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`b . ` `x/(-26)=7/2`

`=>` `2x=-182`

`=>` `x=-91`

Vậy `x=-91`

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`c . ` `|x-1/2|-1/3=5/6`

`=>` `|x-1/2|=5/6+1/3`

`=>` `|x-1/2|=7/6`

`=>` $\left[\begin{matrix} x-\dfrac{1}{2}=\dfrac{7}{6}\\ x-\dfrac{1}{2}=-\dfrac{7}{6}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{7}{6}+\dfrac{1}{2}\\ x=-\dfrac{7}{6}+\dfrac{1}{2}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{5}{3}\\ x=-\dfrac{2}{3}\end{matrix}\right.$

Vậy `x \in {5/3 ; -2/3}`

`#me`