\(\left(n+4\right)\text{⋮}\left(n-1\right)\)
\(\left[\left(n-1\right)+5\right]\text{⋮}\left(n-1\right)\)
Vì \(\left(n-1\right)\text{⋮}\left(n-1\right)\)
⇒ \(5\text{⋮}\left(n-1\right)\)
⇔ \(\left(n-1\right)\) ∈ \(Ư\left(5\right)=\left\{1;5\right\}\)
n-1 1 5
n 2 6


