2.
\(a^2+3a+5⋮a+3\)
\(\Leftrightarrow a\left(a+3\right)+5⋮a+3\)
\(\Leftrightarrow5⋮a+3\)
\(\Leftrightarrow a+3\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)
\(\Leftrightarrow a\in\left\{-2;-4;2;-8\right\}\)
1: \(\Leftrightarrow4a-8+11⋮a-2\)
\(\Leftrightarrow a-2\in\left\{1;-1;11;-11\right\}\)
hay \(a\in\left\{3;1;13;-9\right\}\)