Ta có :
\(3+n⋮n\)
\(n⋮n\)
\(\Rightarrow3+n-n⋮n\)
\(3⋮n\)
\(\Rightarrow n\in\text{Ư}\left(3\right)\)
\(\Rightarrow n\in\left\{1;-1;3;-3\right\}\)
\(\left(3+n\right)⋮n\)
Mà \(n⋮n\)
\(\Rightarrow3⋮n\)
\(\Rightarrow n\in B\left(3\right)=\left\{\pm1;\pm3\right\}\)
\(\Rightarrow n\in\left\{\pm1;\pm3\right\}\)
@Bảo
#Cafe