Nếu ba đường thẳng \(\;{d_1}:{\rm{ }}2x + y-4 = 0\...

D

- Hướng dẫn giải

\(\left\{ \begin{array}{l} \;{d_1}:{\rm{ }}2x + y--4 = 0\\ {d_2}:5x-2y + 3 = 0 \end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l} x = \frac{5}{9}\\ y = \frac{{26}}{9} \end{array} \right. \to {d_1} \cap {d_2} = A\left( {\frac{5}{9};\frac{{26}}{9}} \right) \in {d_3}\)

\( \to \frac{{5m}}{9} + \frac{{26}}{3} - 2 = 0 \Leftrightarrow m = - 12.\)