Answer 1

a, Thay \(x=2;y=-1\Leftrightarrow-1=\left(2m-1\right)2+n\Leftrightarrow4m+n=1\)

Thay \(x=1;y=4\Leftrightarrow4=2m-1+n\Leftrightarrow2m+n=5\)

\(\Leftrightarrow\left\{{}\begin{matrix}4m+n=1\\2m+n=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m=-2\\n=9\end{matrix}\right.\)

b, Vì (d)//(d') nên \(\left\{{}\begin{matrix}m+3=4\\m\ne-1\end{matrix}\right.\Leftrightarrow m=1\)