Đáp án:
\(\left\{ \begin{array}{l}
y = \dfrac{5}{{m + 2}}\\
x = \dfrac{{3m + 1}}{{m + 2}}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
\left\{ \begin{array}{l}
x + y = 3\\
2x - my = 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
2x + 2y = 6\\
2x - my = 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\left( {2 + m} \right)y = 5\\
x = 3 - y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = \dfrac{5}{{m + 2}}\\
x = 3 - \dfrac{5}{{m + 2}}
\end{array} \right.\left( {DK:m \ne - 2} \right)\\
\to \left\{ \begin{array}{l}
y = \dfrac{5}{{m + 2}}\\
x = \dfrac{{3m + 6 - 5}}{{m + 2}}
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = \dfrac{5}{{m + 2}}\\
x = \dfrac{{3m + 1}}{{m + 2}}
\end{array} \right.
\end{array}\)
