a) \(4n-5⋮n\)
\(=>5⋮n\) Vì \(4n⋮n\)
\(=>n\inƯ\left(5\right)=\left\{-1;1;-5;5\right\}\)
Vậy \(n\in\left\{-1;1;-5;5\right\}\)thì \(4n-5⋮n\)
b) \(-11\) là bội của \(n-3\)
\(=>-11⋮n-3\)
\(=>n-3\inƯ\left(-11\right)=\left\{-1;1;-11;11\right\}\)
\(=>n\in\left\{2;4;-8;14\right\}\)
\(\)