Giải:
Vì \(12⋮\left(n-1\right)\)
\(\Leftrightarrow n-1\inƯ\left(12\right)\)
\(\Leftrightarrow n-1\in\left\{1;2;3;4;6;12\right\}\)
\(\Leftrightarrow n\in\left\{2;3;4;5;7;13\right\}\)
Vậy ...
Chúc bạn học tốt!
\(12⋮n-1\)
\(\Rightarrow n-1\inƯ\left(12\right)\)
\(Ư\left(12\right)=\left\{\pm1;\pm2;\pm3;\pm4;\pm6;\pm12\right\}\)
\(\Rightarrow\left\{{}\begin{matrix}n-1=1\Rightarrow n=2\\n-1=-1\Rightarrow n=0\\n-1=2\Rightarrow n=3\\n-1=-2\Rightarrow n=-1\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}n-1=3\Rightarrow n=4\\n-1=-3\Rightarrow n=-2\\n-1=4\Rightarrow n=5\\n-1=-4\Rightarrow n=-3\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}n-1=6\Rightarrow n=7\\n-1=-6\Rightarrow n=-5\\n-1=12\Rightarrow n=13\\n-1=-12\Rightarrow n=-11\end{matrix}\right.\)
Bài làm
Ta có : 12 \(⋮\) ( n-1)
=> n-1 \(\in\) Ư(12)
=> n-1 \(\in\) { 1;2;3;4;6;12}
=> n \(\in\) { 2;3;4;5;6;7;13}
Vậy n \(\in\) { 2;3;4;5;6;7;13} thì 12\(⋮\) (n-1)
