Question

tìm số nguyên x,y sao cho x-y-xy=0

Answer 1

Có: \(x-y-xy=0\)

\(x\left(y-1\right)-\left(y-1\right)=1\)

\(\left(x-1\right)\left(y-1\right)=1\)

\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-1=1\\y-1=1\end{matrix}\right.\\\left\{{}\begin{matrix}x-1=-1\\y-1=-1\end{matrix}\right.\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=2\\y=2\end{matrix}\right.\\\left\{{}\begin{matrix}x=0\\y=0\end{matrix}\right.\end{matrix}\right.\)

Vậy x = 0 và y = 0 hoặc x = 2 và y = 2.