\(n^2+3⋮n+1\)
Mà \(n+1⋮n+1\)
\(\Leftrightarrow\left\{{}\begin{matrix}n^2+3⋮n+1\^2+1⋮n+1\end{matrix}\right.\)
\(\Leftrightarrow2⋮n+1\)
\(\Leftrightarrow n+1\inƯ\left(2\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}n+1=1\+1=2\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}n=0\=1\end{matrix}\right.\)
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