Tìm x, biết: 3x(x ‒ 1) + x ‒ 1 = 0.

3x(x ‒ 1) + x ‒ 1 = 0

⇒ 3x(x ‒ 1) + (x ‒ 1) = 0

⇒ (3x + 1)(x ‒ 1) = 0

\[ \Rightarrow \left[ \begin{array}{l}3x + 1 = 0\\x - 1 = 0\end{array} \right.\]\[ \Rightarrow \left[ \begin{array}{l}x = \frac{{ - 1}}{3}\\x = 1\end{array} \right.\]