\[ \boxed { {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) -2\,ay \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =0} \]
Mathematica: cpu = 0.065008 (sec), leaf count = 46 \[ \left \{\left \{y(x)\to \frac {\sqrt {c_1} \tan \left (\sqrt {a} \sqrt {c_1} x+\sqrt {a} \sqrt {c_1} c_2\right )}{\sqrt {a}}\right \}\right \} \]
Maple: cpu = 0.062 (sec), leaf count = 29 \[ \left \{ y \left ( x \right ) ={\frac {1}{a}\tan \left ( {\it \_C2}\, \sqrt {{\it \_C1}\,a}+x\sqrt {{\it \_C1}\,a} \right ) \sqrt {{\it \_C1} \,a}} \right \} \]