Đáp án:
$\begin{array}{l}
a)m = 1\\
\Rightarrow \left\{ \begin{array}{l}
- x + y = 3 - 1\\
x - 2y = 2
\end{array} \right.\\
\Rightarrow \left\{ \begin{array}{l}
- x + y = 2\\
x - 2y = 2
\end{array} \right.\\
\Rightarrow - x + y + x - 2y = 4\\
\Rightarrow - y = 4\\
\Rightarrow y = - 4\\
Do:x - 2y = 2\\
\Rightarrow x = 2y + 2 = - 6\\
Vay\,\left( {x;y} \right) = \left( { - 6; - 4} \right)\,khi\,m = 1\\
b)2x + y = 3\\
\Rightarrow \left\{ \begin{array}{l}
2x + y = 3\\
x - 2y = 2
\end{array} \right. \Rightarrow \left\{ \begin{array}{l}
x = \frac{8}{5}\\
y = - \frac{1}{5}
\end{array} \right.\\
Do: - x + y = 3m - 1\\
\Rightarrow - \frac{8}{5} - \frac{1}{5} = 3m - 1\\
\Rightarrow m = - \frac{4}{{15}}
\end{array}$
