\(I=\int\limits^1_0\frac{x^3+2x^2+3}{x+2}dx=\int\limits^1_0\left(x^2+\frac{3}{x+2}\right)dx=\left(\frac{x^3}{3}+3ln\left|x+2\right|\right)|^1_0\)
\(=\left(\frac{1}{3}+3ln3\right)-3ln2=\frac{1}{3}+3ln\frac{3}{2}\)
\(\Rightarrow a=b=3\Rightarrow S=18\)