\[ y(x) \left (a^2+\frac {a f'(x)}{f(x)}-b^2 f(x)^2\right )-y'(x) \left (2 a+\frac {f'(x)}{f(x)}\right )+y''(x)=0 \] ✓ Mathematica : cpu = 0.0543663 (sec), leaf count = 49
\[\left \{\left \{y(x)\to c_1 \exp \left (b \int _1^xf(K[1])dK[1]+a x\right )+c_2 \exp \left (a x-b \int _1^xf(K[2])dK[2]\right )\right \}\right \}\] ✓ Maple : cpu = 0.871 (sec), leaf count = 74
\[ \left \{ y \left ( x \right ) ={{\rm e}^{\int \!-{ \left ( {\frac {f \left ( x \right ) \left ( {{\rm e}^{{\it \_C1}\,b}} \right ) ^{2}b}{ \left ( {{\rm e}^{b\int \!f \left ( x \right ) \,{\rm d}x}} \right ) ^{2}}}+bf \left ( x \right ) -{\frac { \left ( {{\rm e}^{{\it \_C1}\,b}} \right ) ^{2}a}{ \left ( {{\rm e}^{b\int \!f \left ( x \right ) \,{\rm d}x}} \right ) ^{2}}}+a \right ) \left ( {\frac { \left ( {{\rm e}^{{\it \_C1}\,b}} \right ) ^{2}}{ \left ( {{\rm e}^{b\int \!f \left ( x \right ) \,{\rm d}x}} \right ) ^{2}}}-1 \right ) ^{-1}}\,{\rm d}x}}{\it \_C2} \right \} \]