Gọi \(d=ƯCLN\left(2n+1;3n+1\right)\left(d\in N\right)\)
\(\Leftrightarrow\left\{{}\begin{matrix}2n+1⋮d\\3n+1⋮d\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}6n+3⋮d\\6n+2⋮d\end{matrix}\right.\)
\(\Leftrightarrow1⋮d\)
Vì \(d\in N;1⋮d\Leftrightarrow d=1\)
\(\LeftrightarrowƯCLN\left(2n+1,3n+1\right)=1\rightarrowđpcm\)