\[ f\left (x^2+y(x)^2\right ) \left (y'(x)^2+1\right )-\left (x y'(x)-y(x)\right )^2=0 \] ✗ Mathematica : cpu = 300. (sec), leaf count = 0 , timed out
$Aborted
✓ Maple : cpu = 2.48 (sec), leaf count = 113
\[ \left \{ y \left ( x \right ) ={x \left ( \tan \left ( {\it RootOf} \left ( -{\it \_Z}+\int ^{{\frac {{x}^{2} \left ( \left ( \tan \left ( {\it \_Z} \right ) \right ) ^{2}+1 \right ) }{ \left ( \tan \left ( {\it \_Z} \right ) \right ) ^{2}}}}\!-{\frac {1}{2\,{\it \_a}\, \left ( f \left ( {\it \_a} \right ) -{\it \_a} \right ) }\sqrt {- \left ( f \left ( {\it \_a} \right ) -{\it \_a} \right ) f \left ( {\it \_a} \right ) }}{d{\it \_a}}+{\it \_C1} \right ) \right ) \right ) ^{-1}},y \left ( x \right ) ={x \left ( \tan \left ( {\it RootOf} \left ( -{\it \_Z}+\int ^{{\frac {{x}^{2} \left ( \left ( \tan \left ( {\it \_Z} \right ) \right ) ^{2}+1 \right ) }{ \left ( \tan \left ( {\it \_Z} \right ) \right ) ^{2}}}}\!{\frac {1}{2\,{\it \_a}\, \left ( f \left ( {\it \_a} \right ) -{\it \_a} \right ) }\sqrt {- \left ( f \left ( {\it \_a} \right ) -{\it \_a} \right ) f \left ( {\it \_a} \right ) }}{d{\it \_a}}+{\it \_C1} \right ) \right ) \right ) ^{-1}} \right \} \]