Cho

- Hướng dẫn giải

Ta có x(3x – 1) – 5(1 – 3x) = 0

ó x(3x – 1) + 5(3x – 1) = 0 ó (3x – 1)(x + 5) = 0

ó $\left[\begin{array}{c}x+5=0\\ 3x-1=0\end{array}\right]$ ó $\left[\begin{array}{c}x=-5\\ 3x=1\end{array}\right]$ ó $\left[\begin{array}{c}x=-5\\ x=\frac{1}{3}\end{array}\right]$

Suy ra

 $$\begin{gathered} x_1=\frac{1}{3}; x_2=-5 \\ \Rightarrow 3x_1-x_2=3.\left(\frac{1}{3}\right)-\left(-5\right)=6 \end{gathered}$$

Đáp án cần chọn là: C