Ta có: \(n^2+n-17\) \(⋮\)\(n-5\)
\(\Rightarrow\) \(n^2-5n+6n-30+13\) \(⋮\)\(n-5\)
\(\Rightarrow\) \(\left(n^2-5n\right)+\left(6n-30\right)+13\) \(⋮\)\(n-5\)
\(\Rightarrow\) \(n\left(n-5\right)+6\left(n-5\right)+13\)
mà \(n-5\) \(⋮\)\(n-5\)
\(\Rightarrow\)\(n\left(n-5\right)\) \(⋮\)\(n-5\)
\(\Rightarrow\)\(6\left(n-5\right)\) \(⋮\) \(n-5\)
Vậy \(13\)\(⋮\)\(n-5\)
\(\Rightarrow\)\(n-5\)\(\in\)\(Ư\left(13\right)\)
Em tự làm tiếp nha