`-3 . |x - 1| = -27`
`|x - 1| = -27 : -3`
`|x - 1| = 9`
`=>` \(\left[ \begin{array}{l}x - 1 = 9\\x - 1 = -9\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 9 + 1\\x = -9 + 1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l} x= 10\\x = -8\end{array} \right.\)
`Vậy: x ∈ {10; -8}`
`@` Ta áp dụng công thức sau: `|x| =a` `=>` \(\left[ \begin{array}{l}x = a\\x = -a\end{array} \right.\)
