Sửa đề :\(\frac{2a+9}{a+3}+\frac{5a+17}{a+3}+\frac{3a}{a+3}\)
\(=\frac{2a+9+5a+17+3a}{a+3}\)
\(=\frac{10a+26}{a+3}\)
\(=\frac{10a+30-4}{a+3}\)
\(\Rightarrow4⋮a+3\)
\(\Rightarrow a+3\in\left(1;-1;2;-2;4;-4\right)\)
\(\Rightarrow a\in\left(-2;-4;-1;-5;1;-7\right)\)