\(\Rightarrow4n-3⋮n-3\)
\(\Rightarrow\left(4n-12\right)+9\)\(⋮n-3\)
\(\Rightarrow4\left(n-3\right)+9\)\(⋮n-3\)
Vì \(n-3\)\(⋮n-3\)
nên \(4\left(n-3\right)\)\(⋮n-3\)
\(\Rightarrow9\)\(⋮n-3\)
\(\Rightarrow n-3\in\left\{1;-1;3;-3;9;-9\right\}\)
\(\Rightarrow n\in\left\{4;2;6;0;12;-6\right\}\)