\(xy+x+2y=5\)
\(\Leftrightarrow x\left(y+1\right)+2y+2=5+2\)
\(\Leftrightarrow x\left(y+1\right)+2\left(y+1\right)=7\)
\(\Leftrightarrow\left(x+2\right)\left(y+1\right)=7\)
Ta có bảng:
x + 2 | 1 | -1 | 7 | -7 |
y + 1 | 7 | -7 | 1 | -1 |
x | -1 | -3 | 5 | -9 |
y | 6 | -8 | 0 | -2 |
Vậy các cặp (x;y) là (-1;6) ; (-3;-8) ; (5;0) ; (-9;-2)