Answer:
\(3n+4\)
\(=\left(3n-3\right)+3+4\)
\(=3.\left(n-1\right)+7\)
Mà: \(3.\left(n-1\right)⋮n-1\)
\(\Rightarrow7⋮n-1\)
\(\Rightarrow n-1\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)
\(\Rightarrow n\in\left\{-6;0;2;8\right\}\)
Mà đề ra: \(n\inℕ\)
\(\Rightarrow n\in\left\{0;2;8\right\}\)
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