a: =>4n+2+5 chia hết cho 2n+1
\(\Leftrightarrow2n+1\in\left\{1;-1;5;-5\right\}\)
hay \(n\in\left\{0;-1;2;-3\right\}\)
b: =>3n-9+11 chia hết cho n-3
\(\Leftrightarrow n-3\in\left\{1;-1;11;-11\right\}\)
hay \(n\in\left\{4;2;14;-8\right\}\)
c: \(\Leftrightarrow7⋮n+2\)
=>\(n+2\in\left\{1;-1;7;-7\right\}\)
hay \(n\in\left\{-1;-3;5;-9\right\}\)
d: \(\Rightarrow n^2-1+2⋮n-1\)
\(\Leftrightarrow n-1\in\left\{1;-1;2;-2\right\}\)
hay \(n\in\left\{2;0;3;-1\right\}\)