Làm câu b nhé, câu a mk chưa gặp bao h
b) Ta có :
\(n^2-6⋮n-3\)
Mà \(n-3⋮n-3\)
\(\Leftrightarrow\left\{{}\begin{matrix}n^2-6⋮n-3\^2-3n⋮n-3\end{matrix}\right.\)
\(\Leftrightarrow3n-6⋮n-3\)
Mà \(n-3⋮n-3\)
\(\Leftrightarrow\left\{{}\begin{matrix}3n-6⋮n-3\\3n-9⋮n-3\end{matrix}\right.\)
\(\Leftrightarrow3⋮n-3\)
Vì \(n\in Z\Leftrightarrow n-3\in Z;n-3\inƯ\left(3\right)\)
\(\Leftrightarrow\left\{{}\begin{matrix}n-3=1\Rightarrow n=4\left(tm\right)\-3=3\Leftrightarrow n=6\left(tm\right)\-3=-1\Leftrightarrow n=-4\left(tm\right)\-3=-3\Leftrightarrow n=-6\left(tm\right)\end{matrix}\right.\)
Vậy =-..
