\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +2\,a{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +f \left ( x \right ) y \left ( x \right ) =0} \]
Mathematica: cpu = 0.329542 (sec), leaf count = 23 \[ \text {DSolve}\left [2 a y'(x)+f(x) y(x)+y''(x)=0,y(x),x\right ] \]
Maple: cpu = 0.0 (sec), leaf count = 28 \[ \left \{ y \left ( x \right ) ={\it DESol} \left ( \left \{ f \left ( x \right ) {\it \_Y} \left ( x \right ) +2\,a{\frac {\rm d}{{\rm d}x}}{ \it \_Y} \left ( x \right ) +{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}{\it \_Y} \left ( x \right ) \right \} , \left \{ {\it \_Y} \left ( x \right ) \right \} \right ) \right \} \]