Hôm nay nghiêm túc đăng bài ghê:^
Bổ sung đk \(x,y\in Z\)
\(\Rightarrow x+y-xy-1=-17\\ \Rightarrow x\left(1-y\right)-\left(1-y\right)=-17\\ \Rightarrow\left(x-1\right)\left(1-y\right)=-17\\ \Rightarrow\left(x-1\right)\left(y-1\right)=17=17.1=\left(-17\right)\left(-1\right)\)
\(\left\{{}\begin{matrix}x-1=17\\y-1=1\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=18\\y=2\end{matrix}\right.\\ \left\{{}\begin{matrix}x-1=1\\y-1=17\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=2\\y=18\end{matrix}\right.\\ \left\{{}\begin{matrix}x-1=-17\\y-1=-1\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=-16\\y=-2\end{matrix}\right.\\ \left\{{}\begin{matrix}x-1=-1\\y-1=-17\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=-2\\y=-16\end{matrix}\right.\)
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