\[ \boxed { \left ( ay \left ( x \right ) +b \right ) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left ( x \right ) +c \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.062008 (sec), leaf count = 36 \[ \left \{\left \{y(x)\to \frac {\left (c_1 (-(a+c)) \left (-c_2-x\right )\right ){}^{\frac {a}{a+c}}-b}{a}\right \}\right \} \]
Maple: cpu = 1.529 (sec), leaf count = 88 \[ \left \{ y \left ( x \right ) =-{\frac {1}{a} \left ( -{\it \_C1}\,ax-{ \it \_C1}\,xc+{b \left ( \left ( {\frac {1}{ \left ( a+c \right ) \left ( {\it \_C1}\,x+{\it \_C2} \right ) }} \right ) ^{{\frac {c}{a} \left ( 1+{\frac {c}{a}} \right ) ^{-1}}} \right ) ^{-1}}-{\it \_C2}\,a- {\it \_C2}\,c \right ) \left ( {\frac {1}{ \left ( a+c \right ) \left ( { \it \_C1}\,x+{\it \_C2} \right ) }} \right ) ^{{\frac {c}{a} \left ( 1+{ \frac {c}{a}} \right ) ^{-1}}}} \right \} \]