a) ta có : \(x-y=7\Leftrightarrow x=7+y\)
thay vào \(x+y=3\Leftrightarrow7+y+y=3\Leftrightarrow y+y=3-7=-4\)
\(\Leftrightarrow2y=-4\Leftrightarrow y=\dfrac{-4}{2}=-2\)
ta có : \(y=-2\Rightarrow x=7+y=7-2=5\) vậy \(y=-2;x=5\)
b) ta có : \(3=1.3=3.1=\left(-1\right).\left(-3\right)=\left(-3\right).\left(-1\right)\)
\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x+3=1\\y-2=3\end{matrix}\right.\\\left\{{}\begin{matrix}x+3=3\\y-2=1\end{matrix}\right.\\\left\{{}\begin{matrix}x+3=-1\\y-2=-3\end{matrix}\right.\\\left\{{}\begin{matrix}x+3=-3\\y-2=-1\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=-2\\y=5\end{matrix}\right.\\\left\{{}\begin{matrix}x=0\\y=3\end{matrix}\right.\\\left\{{}\begin{matrix}x=-4\\y=-1\end{matrix}\right.\\\left\{{}\begin{matrix}x=-6\\y-1\end{matrix}\right.\end{matrix}\right.\) (tmđk)
vậy ........................................................................................
