khi x-1\(\ge\)0\(\Leftrightarrow\)x\(\ge\)1
ta có pt x-1=3x+2
\(\Leftrightarrow\)x-3x=2+1
\(\Leftrightarrow\)-2x=3
\(\Leftrightarrow\)x=\(\frac{-3}{2}\)(loại)
khi x-1<0\(\Leftrightarrow\)x<1
ta có pt -x+1=3x+2
\(\Leftrightarrow\)-x-3x=2-1
\(\Leftrightarrow\)-4x=1
\(\Leftrightarrow\)x=\(\frac{-1}{4}\)(nhận)
vậy s={\(\frac{-1}{4}\)}