Bài 2
\(a,\left\{{}\begin{matrix}2x+y=5\\x-y=1\end{matrix}\right.=>\left\{{}\begin{matrix}3x=6\\x-y=1\end{matrix}\right.=>\left\{{}\begin{matrix}x=2\\2-y=1\end{matrix}\right.=>\left\{{}\begin{matrix}x=2\\y=1\end{matrix}\right.\)
Vậy \(\left(x;y\right)=\left(2;1\right)\)
\(b,\left\{{}\begin{matrix}0,1x+0,2y=2\\x+2y=20\end{matrix}\right.=>\left\{{}\begin{matrix}0,1x+0,2y=2\\0,1x+0,2y=2\end{matrix}\right.\)
Vậy pt có vô số nghiệm
\(c,\left\{{}\begin{matrix}3x-2y=12\\6x-4y=20\end{matrix}\right.=>\left\{{}\begin{matrix}3x-2y=12\\3x-2y=10\end{matrix}\right.\)
=> pt vô nghiệm
Vậy pt vô nghiệm