\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) +f \left ( x \right ) \left ( \left ( y \left ( x \right ) \right ) ^{2}+2\,ay \left ( x \right ) +b \right ) =0} \]
Mathematica: cpu = 0.057507 (sec), leaf count = 60 \[ \left \{\left \{y(x)\to \sqrt {b-a^2} \tan \left (\sqrt {b-a^2} \int _1^x -f(K[1]) \, dK[1]+c_1 \sqrt {b-a^2}\right )-a\right \}\right \} \]
Maple: cpu = 0.031 (sec), leaf count = 45 \[ \left \{ y \left ( x \right ) =\tanh \left ( \int \!f \left ( x \right ) \,{\rm d}x\sqrt {{a}^{2}-b}+{\it \_C1}\,\sqrt {{a}^{2}-b} \right ) \sqrt {{a}^{2}-b}-a \right \} \]
Sage: cpu = 0 (sec), leaf count = 0 \[ \text {Maxima was unable to solve this ODE} \]