(n-1)(2n+3)=6
\(\Leftrightarrow2n^2+3n-2n-3=6\)
\(\Leftrightarrow2n^2+n-3=6\)
\(\Leftrightarrow2n^2-2n+3n-3=6\)
\(\Leftrightarrow2n\left(n-1\right)+3\left(n-1\right)=6\)
\(\Leftrightarrow\left(n-1\right)\left(2n-3\right)=6\)
Xong rồi bạn để từng cái bằng -1,-6,-2,-3,1,6,2,3
(n-1) . (2n+3)= 6= 6.1= 1.6= (-1).(-6)=(-6).(-1)
Lập bảng:
| n-1 | 6 | 1 | -1 | -6 |
| n | 7 | 2 | 0 | -5 |
| 2n+3 | 1 | 6 | -6 | -1 |
| 2n | -2 | 3 | -9 | -4 |
| n | -1 | \(\frac{3}{2}\) | \(\frac{-9}{2}\) | -2 |
Vậy x, y \(\in\) {(7; -1); (-5; -2)}
