Hệ phương trình \(\left\{ \...

A

- Hướng dẫn giải

 $\begin{array}{l}\,\,\left\{ \begin{array}{l}2x + 18y = - 9\\4x + 18y = - 27\end{array} \right. \\ \Leftrightarrow \left\{ \begin{array}{l}2x = - 18\\2x + 18y = - 9\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}x = - 9\\2.\left( { - 9} \right) + 18y = - 9\end{array} \right. \\ \Leftrightarrow \left\{ \begin{array}{l}x = - 9\\18y = 9\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}x = - 9\\y = \dfrac{1}{2}\end{array} \right.\end{array}$

⇒ m : n = -18