\[ \boxed { \left ( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) \right ) y \left ( x \right ) + \left ( y \left ( x \right ) \right ) ^{2}-ax-b=0} \]
Mathematica: cpu = 0.039505 (sec), leaf count = 72 \[ \left \{\left \{y(x)\to -\frac {\sqrt {a x^3+3 b x^2+3 c_2 x+6 c_1}}{\sqrt {3}}\right \},\left \{y(x)\to \frac {\sqrt {a x^3+3 b x^2+3 c_2 x+6 c_1}}{\sqrt {3}}\right \}\right \} \]
Maple: cpu = 1.669 (sec), leaf count = 0 \[ \text {could not solve} \]