\[ f\left (a y(x)^2+x^2\right ) \left (a y(x) y'(x)+x\right )-x y'(x)-y(x)=0 \] ✓ Mathematica : cpu = 201.488 (sec), leaf count = 88
\[\text {Solve}\left [\int _1^{y(x)} \left (-\int _1^x \left (1-2 a K[1] K[2] f'\left (a K[2]^2+K[1]^2\right )\right ) \, dK[1]-a K[2] f\left (a K[2]^2+x^2\right )+x\right ) \, dK[2]+\int _1^x \left (y(x)-K[1] f\left (K[1]^2+a y(x)^2\right )\right ) \, dK[1]=c_1,y(x)\right ]\]
✓ Maple : cpu = 0.071 (sec), leaf count = 45
\[ \left \{ -{ax \left ( y \left ( x \right ) \right ) ^{2}{\frac {1}{\sqrt {{a}^{2} \left ( y \left ( x \right ) \right ) ^{2}}}}}-\int ^{-{\frac {a \left ( y \left ( x \right ) \right ) ^{2}}{2}}-{\frac {{x}^{2}}{2}}}\!f \left ( -2\,{\it \_a} \right ) {d{\it \_a}}+{\it \_C1}=0 \right \} \]