x( y +1) - ( y + 1) =10

Ta có: `x(y + 1) - (y + 1) = 10`

`=> (x - 1)(y + 1) = 10`

`=> 10 \vdots x - 1`

`=> x - 1 \in Ư(10)`

`=> x - 1 \in {+-1,+-2,+-5,+-10}`

Ta có bảng sau:

\begin{array}{|c|c|c|}\hline \text{x - 1}&\text{1}&\text{-1}&\text{2}&\text{-2}&\text{5}&\text{-5}&\text{10}&\text{-10}\\\hline \text{y + 1}&\text{10}&\text{-10}&\text{5}&\text{-5}&\text{2}&\text{-2}&\text{1}&\text{-1}\\\hline \text{x}&\text{2}&\text{0}&\text{3}&\text{-1}&\text{6}&\text{-4}&\text{11}&\text{-9}\\\hline \text{y}&\text{9}&\text{-11}&\text{4}&\text{-6}&\text{1}&\text{-3}&\text{0}&\text{-2}\\\hline \text{kết luận}&\text{chọn}&\text{chọn}&\text{chọn}&\text{chọn}&\text{chọn}&\text{chọn}&\text{chọn}&\text{chọn}\\\hline\end{array}

Vậy `(x,y) \in {(2,9);(0,-11);(3,4);(-1,-6);(6,1);(-4,-3);(11,0);(-9,2)}`

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