|3x| = -2x + 1
⇔ \(\left[ \begin{array}{l}3x=-2x+1\\3x=2x-1\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}3x+2x=1\\3x-2x=-1\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}5x=1\\x=-1\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=1/5\\x=-1\end{array} \right.\)
Vậy pt có tập nghiệm: S = {1/5; -1}