\[ y(x) y''(x)-a y'(x)^2=0 \] ✓ Mathematica : cpu = 0.0426184 (sec), leaf count = 26
\[\left \{\left \{y(x)\to c_2 \left (-a x-c_1+x\right ){}^{\frac {1}{1-a}}\right \}\right \}\]
✓ Maple : cpu = 0.08 (sec), leaf count = 25
\[ \left \{ y \left ( x \right ) = \left ( {\frac {1}{ \left ( 1-a \right ) \left ( {\it \_C1}\,x+{\it \_C2} \right ) }} \right ) ^{ \left ( a-1 \right ) ^{-1}} \right \} \]