(x + 1)(y + 2) = 7
\(\Rightarrow\) (x +1)(y + 2) = 1.7 = 7.1 = (-1).(-7) = (-7).(-1)
Ta có bảng sau :
| x + 1 | 1 | 7 | -1 | -7 |
| y + 2 | 7 | 1 | -7 | -1 |
| x | 0 | 6 | -2 | -8 |
| y | 5 | -1 | -9 | -3 |
\(\Rightarrow\left\{{}\begin{matrix}x=0\\y=5\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=6\\y=-1\end{matrix}\right.\Rightarrow}\left\{{}\begin{matrix}x=-2\\y=-9\end{matrix}\right.\Rightarrow}\left\{{}\begin{matrix}x=-8\\y=-3\end{matrix}\right.\)
( x + 1) . ( y + 2) = 7
\(\Rightarrow\)( x + 1) . ( y + 2) \(\in\)Ư( 7 )
Ư(7) = 1.7 = -1 . (-7)
| x + 1 | 1 | 7 | -1 | -7 |
| x | 0 | 6 | -2 | -8 |
| y + 2 | 7 | 1 | -7 | -1 |
| y | 5 | -1 | -9 | -3 |
Vậy ( x,y) = { ( 0;5 ); ( 6;-1 ); ( -2;-9 ); ( -8; -3)
(x+1).(y+2)=7
\(\Rightarrow\left(x+1\right);\left(y+2\right)\inƯ\left(7\right)\)
\(\Rightarrow x+1;y+2\in\left\{-7;-1;1;7\right\}\)
Ta có bảng sau:
\(\begin{matrix}x+1&-7&-1&1&7\\y+2&-1&-7&7&1\\x&-8&-2&0&6\\y&-3&-9&5&-1\end{matrix}\)
Vậy \(\left(x;y\right)\in\left\{\left(-8;-3\right);\left(-2;-9\right);\left(0;5\right);\left(6;-1\right)\right\}\)Chúc bạn học tốt nha!!!