Question

tìm số nguyên x,y thỏa mản x+y+xy=2

Answer 1

\(\Leftrightarrow\left(x+1\right)\left(y+1\right)=3\)

\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x+1=1\Leftrightarrow x=0\\y+1=3\Leftrightarrow y=2\end{matrix}\right.\\\left\{{}\begin{matrix}x+1=-1\Leftrightarrow x=-2\\y+1=-3\Leftrightarrow y=-4\end{matrix}\right.\\\left\{{}\begin{matrix}x+1=3\Leftrightarrow x=2\\y+1=1\Leftrightarrow y=0\end{matrix}\right.\\\left\{{}\begin{matrix}x+1=-3\Leftrightarrow x=-4\\y+1=-1\Leftrightarrow y=-2\end{matrix}\right.\end{matrix}\right.\)