Đáp án:
\(\left[ \begin{array}{l}
m = 2\\
m = \dfrac{3}{2}
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
\left\{ \begin{array}{l}
x = y - 2m + 1\\
m\left( {y - 2m + 1} \right) + y = m + 3
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = y - 2m + 1\\
my - 2{m^2} + m + y = m + 3\left( 1 \right)
\end{array} \right.\\
\left( 1 \right) \to \left( {m + 1} \right)y = 2{m^2} + 3\\
\to y = \dfrac{{2{m^2} + 3}}{{m + 1}}\\
\to x = \dfrac{{2{m^2} + 3}}{{m + 1}} - 2m + 1\\
= \dfrac{{2{m^2} + 3 - 2{m^2} - 2m + m + 1}}{{m + 1}}\\
= \dfrac{{4 - m}}{{m + 1}}\\
DK:m \ne - 1\\
Có:2x + y = 5\\
\to 2.\dfrac{{4 - m}}{{m + 1}} + \dfrac{{2{m^2} + 3}}{{m + 1}} = 5\\
\to 8 - 2m + 2{m^2} + 3 = 5m + 5\\
\to 2{m^2} - 7m + 6 = 0\\
\to \left[ \begin{array}{l}
m = 2\\
m = \dfrac{3}{2}
\end{array} \right.
\end{array}\)
