\[ (3 a+b x) y'(x)+a x y''(x)+3 b y(x)=0 \] ✓ Mathematica : cpu = 0.129106 (sec), leaf count = 70
\[\left \{\left \{y(x)\to \frac {c_2 e^{-\frac {b x}{a}} \left (b^2 x^2 \text {Ei}\left (\frac {b x}{a}\right )-a e^{\frac {b x}{a}} (a+b x)\right )}{2 a^2 x^2}+c_1 e^{-\frac {b x}{a}}\right \}\right \}\]
✓ Maple : cpu = 0.054 (sec), leaf count = 55
\[ \left \{ y \left ( x \right ) ={\frac {1}{{x}^{2}} \left ( {\it Ei} \left ( 1,-{\frac {bx}{a}} \right ) {{\rm e}^{-{\frac {bx}{a}}}}{\it \_C2}\,{b}^{2}{x}^{2}+{\it \_C1}\,{{\rm e}^{-{\frac {bx}{a}}}}{x}^{2}+a{\it \_C2}\, \left ( bx+a \right ) \right ) } \right \} \]