Tìm x,y ∈ `ZZ` biết : ( x - 1 ) ( y + 5 ) = 7

Đáp án:

`( x - 1 ).( y + 5 ) = 7`

Vì `x,y ∈ ZZ`

`-> x - 1, y + 5 ∈ ZZ`

`-> x - 1. y + 5 ∈ Ư_{(7)} = {1; -1;7;-7}`

Lập bảng giá trị

              \begin{array}{|c|c|c|}\hline \text{x - 1}&\text{1}&\text{-1}&\text{7}&\text{-7}\\\hline \text{y + 5}&\text{7}&\text{-7}&\text{1}&\text{-1}\\\hline \text{x}&\text{2}&\text{0}&\text{8}&\text{-6}\\\hline \text{y}&\text{2}&\text{-12}&\text{-4}&\text{-6}\\\hline\end{array}

Vậy `(x,y) = (2,2);(0,-12);(8, -4); (-6,-6)`

$#dairana$