Giải thích các bước giải:
\(\begin{array}{l}
a.m = - \frac{1}{2}\\
\to \left\{ \begin{array}{l}
2x - y = 3\\
y = - \frac{1}{2}
\end{array} \right. \to \left\{ \begin{array}{l}
x = \frac{5}{4}\\
y = - \frac{1}{2}
\end{array} \right.\\
b.m = 1\\
\to \left\{ \begin{array}{l}
2x - y = 3\\
x + y = - \frac{1}{2}
\end{array} \right. \to \left\{ \begin{array}{l}
3x = \frac{5}{2}\\
x + y = - \frac{1}{2}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \frac{5}{6}\\
y = - \frac{4}{3}
\end{array} \right.\\
c.\left\{ \begin{array}{l}
x = 1 - y\\
2x - y = 3\\
\left( {2m - 1} \right)x + y = - \frac{1}{2}
\end{array} \right. \to \left\{ \begin{array}{l}
x = 1 - y\\
\left( {2m + 1} \right)\left( {1 - y} \right) = \frac{5}{2}\\
2 - 2y - y = 3
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = 1 - y\\
y = - \frac{1}{3}\\
m = \frac{7}{{16}}
\end{array} \right.\\
\to m = \frac{7}{{16}}
\end{array}\)
