x/7 = -6/21 | x - 1/5 | - 1/2 = 0

Đáp án + Giải thích các bước giải:

`x/7 = - 6/21`

`⇔` `x/7 =` $\dfrac{-6:3}{21:3}$ 

`⇔` `x/7 = - 2/7`

`=>` `x = - 2`

`Vậy` `x = - 2`

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`| x - 1/5 | - 1/2 = 0`

`⇔` `| x - 1/5 | = 1/2`

`⇔` \(\left[ \begin{array}{l}x-\dfrac{1}{5}=\dfrac{1}{2}\\x-\dfrac{1}{5}=-\dfrac{1}{2}\end{array} \right.\) 

`⇔` \(\left[ \begin{array}{l}x=\dfrac{1}{2}+\dfrac{1}{5}\\x=-\dfrac{1}{2}+\dfrac{1}{5}\end{array} \right.\) 

`⇔` \(\left[ \begin{array}{l}x=\dfrac{7}{10}\\x=-\dfrac{3}{10}\end{array} \right.\) 

`Vậy` `x = 7/10 ; x = - 3/10`