\[ f(x) y(x)-g(x)+y''(x)+3 y(x) y'(x)+y(x)^3=0 \] ✗ Mathematica : cpu = 8.27316 (sec), leaf count = 0 , could not solve
DSolve[-g[x] + f[x]*y[x] + y[x]^3 + 3*y[x]*Derivative[1][y][x] + Derivative[2][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0 , result contains DESol
\[ \left \{ y \left ( x \right ) ={\frac {{\frac {\rm d}{{\rm d}x}}{\it DESol} \left ( \left \{ -g \left ( x \right ) {\it \_Y} \left ( x \right ) +f \left ( x \right ) {\frac {\rm d}{{\rm d}x}}{\it \_Y} \left ( x \right ) +{\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}{\it \_Y} \left ( x \right ) \right \} , \left \{ {\it \_Y} \left ( x \right ) \right \} \right ) }{{\it DESol} \left ( \left \{ -g \left ( x \right ) {\it \_Y} \left ( x \right ) +f \left ( x \right ) {\frac {\rm d}{{\rm d}x}}{\it \_Y} \left ( x \right ) +{\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}{\it \_Y} \left ( x \right ) \right \} , \left \{ {\it \_Y} \left ( x \right ) \right \} \right ) }} \right \} \]