2n - 1 \(⋮\) n - 3
\(\Rightarrow\) 2n - 3 + 3 - 1 \(⋮\) n - 3
\(\Rightarrow\) 2n - 3 + 4 \(⋮\) n - 3
Vì 2n - 3 \(⋮\) n - 3 nên để 2n - 3 + 4 \(⋮\) n - 3
\(\Rightarrow\) 4 \(⋮\) n - 3 \(\Rightarrow\) n - 3 \(\in\) Ư ( 4 ) = \(\left\{1;2;4\right\}\)
Ta có bảng
n - 3 | 1 | 2 | 4 |
n | 4 | 5 | 7 |
Vậy n \(\in\) \(\left\{4;5;7\right\}\)