Nếu ba đường thẳng \({d_1}:...

D

- Hướng dẫn giải

\(\begin{array}{l}\left\{ \begin{array}{l}\;{d_1}:{\rm{ }}2x + y--4 = 0\\{d_2}:5x--2y + 3 = 0\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}x = \frac{5}{9}\\y = \frac{{26}}{9}\end{array} \right.\\ \Rightarrow {d_1} \cap {d_2} = A\left( {\frac{5}{9};\frac{{26}}{9}} \right) \in {d_3}\\ \Rightarrow \frac{{5m}}{9} + \frac{{26}}{3} - 2 = 0\\ \Leftrightarrow m = - 12.\end{array}\)