Đáp án:
Gọi $UCLN (2n + 3, n + 1) = d$
`->` \(\left\{ \begin{array}{l}2n + 3 \vdots d\\n + 1 \vdots d\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}2n + 3 \vdots d\\2 (n + 1) \vdots d\end{array} \right.\)
`->` \(\left\{ \begin{array}{l}2n + 3 \vdots d\\2n + 2 \vdots d\end{array} \right.\)
`-> 2n + 3 - 2n - 2 \vdots d`
`-> 1 \vdots d`
`-> (2n ) 3)/(n + 1)` tối giản