\[ (3 a+b x) y'(x)+a x y''(x)+3 b y(x)=0 \] ✓ Mathematica : cpu = 0.112558 (sec), leaf count = 63
\[\left \{\left \{y(x)\to \frac {1}{2} \left (\frac {b^2 c_2 e^{-\frac {b x}{a}} \text {Ei}\left (\frac {b x}{a}\right )}{a^2}-\frac {c_2 (a+b x)}{a x^2}+2 c_1 e^{-\frac {b x}{a}}\right )\right \}\right \}\]
✓ Maple : cpu = 0.1 (sec), leaf count = 55
\[ \left \{ y \left ( x \right ) ={\frac {1}{{x}^{2}} \left ( {\it Ei} \left ( 1,-{\frac {bx}{a}} \right ) {{\rm e}^{-{\frac {bx}{a}}}}{\it \_C2}\,{b}^{2}{x}^{2}+{\it \_C1}\,{{\rm e}^{-{\frac {bx}{a}}}}{x}^{2}+a{\it \_C2}\, \left ( bx+a \right ) \right ) } \right \} \]