\[ \boxed { \left ( {x}^{2}+a \right ) \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}-2\,xy \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) + \left ( y \left ( x \right ) \right ) ^{2}+b=0} \]
Mathematica: cpu = 0 (sec), leaf count = 0 \[ \text {Hanged} \]
Maple: cpu = 0.561 (sec), leaf count = 78 \[ \left \{ y \left ( x \right ) ={\frac {1}{a}\sqrt {-ab \left ( {x}^{2}+a \right ) }},y \left ( x \right ) =-{\frac {1}{a}\sqrt {-ab \left ( {x}^{2 }+a \right ) }},y \left ( x \right ) ={\it \_C1}\,x-\sqrt {-a{{\it \_C1}} ^{2}-b},y \left ( x \right ) ={\it \_C1}\,x+\sqrt {-a{{\it \_C1}}^{2}-b} \right \} \]