Bổ sung đề : `x,y in ZZ` nếu không thì dài lắm.
`xy-2x=5`
`-> x(y-2) = 5`
Do `x,y in Z`
`-> x ; y-2 in ZZ`
`->` Ta có : `x(y-2) = 5 = 5.1 = (-5).(-1)`
* Ta có bảng :
$\begin{array}{|c|c|c|}\hline \text{x}&\text{1}&\text{5}&\text{-1}&\text{-5}\\\hline \text{y-2}&\text{5}&\text{1}&\text{-5}&\text{-1}\\\hline \text{y}&\text{7}&\text{3}&\text{-3}&\text{1}\\\hline \text{KL}&\text{TM}&\text{TM}&\text{TM}&\text{TM}\\\hline\end{array}$
Vậy `(x,y) in {(1,7);(5,3);(-1,-3);(-5,1)}`
