\[ a y'(x)+b y(x)+y''(x)=0 \] ✓ Mathematica : cpu = 0.0061069 (sec), leaf count = 47
\[\left \{\left \{y(x)\to e^{-\frac {1}{2} x \left (\sqrt {a^2-4 b}+a\right )} \left (c_2 e^{x \sqrt {a^2-4 b}}+c_1\right )\right \}\right \}\]
✓ Maple : cpu = 0.014 (sec), leaf count = 41
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{-{\frac {x}{2} \left ( a-\sqrt {{a}^{2}-4\,b} \right ) }}}+{\it \_C2}\,{{\rm e}^{-{\frac {x}{2} \left ( a+\sqrt {{a}^{2}-4\,b} \right ) }}} \right \} \]