a) \(\left\{{}\begin{matrix}x+y=1\\2x-y=m-1\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x+y=1\\3x=m\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}y=1-x\\x=\frac{m}{3}\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}y=1-\frac{m}{3}=\frac{2}{3}m\\x=\frac{m}{3}\end{matrix}\right.\)
Vậy \(x=\frac{m}{3};y=\frac{2m}{3}\)
b) Để x,y là số nguyên thì m chia hết cho 3