tìm các số nguyên x,y sao cho xy-x -y = 2 nhanh hộ mk với

`xy - x - y = 2`

`⇒ x . ( y - 1 ) - y = 2`

`⇒ x . ( y - 1 ) - y + 1 = 2 + 1`

`⇒ x . ( y - 1 ) - ( y - 1 ) = 3`

`⇒ ( y - 1 ) . ( x - 1 ) = 3 = 1 . 3 = ( - 1 ) . ( - 3 )`

Ta có bảng sau `:`

\begin{array}{|c|c|c|}\hline \text{y - 1}&\text{1}&\text{3}&\text{- 1}&\text{- 3}\\\hline \text{x - 1}&\text{3}&\text{1}&\text{- 3}&\text{- 1}\\\hline \text{y}&\text{2}&\text{4}&\text{0}&\text{- 2}\\\hline \text{x}&\text{4}&\text{2}&\text{- 2}&\text{0}\\\hline\end{array}

Vậy `, ( x ; y ) ∈ { ( 2 ; 4 ) ; ( 4 ; 2 ) ; ( 0 ; - 2 ) ; ( - 2 ; 0 ) }`