\[ (3 a+b x) y'(x)+a x y''(x)+3 b y(x)=0 \] ✓ Mathematica : cpu = 0.110397 (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 = 0.051 (sec), leaf count = 49
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{-{\frac {bx}{a}}}}+{\it \_C2}\, \left ( {\frac {a \left ( bx+a \right ) }{{x}^{2}}}+{{\rm e}^{-{\frac {bx}{a}}}}{\it Ei} \left ( 1,-{\frac {bx}{a}} \right ) {b}^{2} \right ) \right \} \]