a, Ta có :
\(n-1⋮n+6\)
Mà \(n+6⋮n+6\)
\(\Leftrightarrow7⋮n+6\)
Vì \(n\in Z\Leftrightarrow n+6\in Z;n+6\inƯ\left(7\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}n+6=1\\n+6=-1\\n+6=7\\n+6=-7\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}n=-5\\n=-7\\n=1\\n=-13\end{matrix}\right.\)
Vậy ..............
b, Ta có :
\(8n-3⋮4n+5\)
Mà \(4n+5⋮4n+5\)
\(\Leftrightarrow\left\{{}\begin{matrix}8n-3⋮4n+5\\8n+10⋮4n+5\end{matrix}\right.\)
\(\Leftrightarrow13⋮4n+5\)
Vì \(n\in Z\Leftrightarrow4n+5\in Z;4n+5\inƯ\left(13\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}4n+5=1\\4n+5=13\\4n+5=-13\\4n+5=-1\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}n=-1\\n=2\\n=-4,5\left(loại\right)\\n=-\dfrac{3}{2}\left(loại\right)\end{matrix}\right.\)
Vậy ....
c,d tương tự
