\[ \boxed { x \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{3}-y \left ( x \right ) \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}+a=0} \]
Mathematica: cpu = 0 (sec), leaf count = 0 \[ \text {Hanged} \]
Maple: cpu = 0.032 (sec), leaf count = 92 \[ \left \{ y \left ( x \right ) ={\frac {3\,\sqrt [3]{2}}{2}\sqrt [3]{a{x} ^{2}}},y \left ( x \right ) =-{\frac {3\,\sqrt [3]{2}}{4}\sqrt [3]{a{x}^ {2}}}-{\frac {3\,i}{4}}\sqrt {3}\sqrt [3]{2}\sqrt [3]{a{x}^{2}},y \left ( x \right ) =-{\frac {3\,\sqrt [3]{2}}{4}\sqrt [3]{a{x}^{2}}}+{ \frac {3\,i}{4}}\sqrt {3}\sqrt [3]{2}\sqrt [3]{a{x}^{2}},y \left ( x \right ) ={\it \_C1}\,x+{\frac {a}{{{\it \_C1}}^{2}}} \right \} \]