\[ -y(x) f'(x)+2 f(x) y'(x)+2 f(x) y(x)^2-2 f(x)^2=0 \] ✓ Mathematica : cpu = 0.0806161 (sec), leaf count = 38
\[\left \{\left \{y(x)\to i \sqrt {f(x)} \tan \left (c_1+i \int _1^x -\sqrt {f(K[1])} \, dK[1]\right )\right \}\right \}\] ✓ Maple : cpu = 0.057 (sec), leaf count = 23
\[ \left \{ y \left ( x \right ) =i\tan \left ( -i\int \!\sqrt {f \left ( x \right ) }\,{\rm d}x+{\it \_C1} \right ) \sqrt {f \left ( x \right ) } \right \} \]