~ Bạn tham khảo ~
`2n^2 - n +2 \vdots 2n+1`
`=> 2n^2 + n - 2n - 1 + 3 \vdots 2n+1`
`=> n(2n+1) - (2n+1) + 3 \vdots 2n+1`
`=> (2n+1)(n-1) + 3 \vdots 2n+1`
Vì `(2n+1)(n-1) \vdots 2n+1`
`=> 3 \vdots 2n+1`
`=> 2n + 1 \in Ư(3)`
`=> 2n + 1 \in {1;3;-1;-3}`
`=> 2n \in {0;2;-2;-4}`
`=> n \in {0;1;-1;-2}`
Vậy `n = {0;1;-1;-2}`