`| 1/2 x + 3/5 | = 1/2`
`⇔` $\left[\begin{matrix}\frac{1}{2} x + \frac{3}{5} = \frac{1}{2}\\\frac{1}{2} x + \frac{3}{5} = \frac{- 1}{2}\end{matrix}\right.$
`⇔` $\left[\begin{matrix}\frac{1}{2} x = \frac{- 1}{10}\\\frac{1}{2} x = \frac{- 11}{10}\end{matrix}\right.$
`⇔` $\left[\begin{matrix}x = \frac{- 1}{5}\\x = \frac{- 11}{5}\end{matrix}\right.$
Vậy `, x ∈ { ( - 1 )/5 ; ( - 11 )/5 } .`