\[ f(x) y(x)-g(x)+y''(x)+3 y(x) y'(x)+y(x)^3=0 \] ✗ Mathematica : cpu = 2.96916 (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
\[\left \{y \left (x \right ) = \frac {\frac {d}{d x}\mathit {DESol}\left (\left \{-\textit {\_Y} \left (x \right ) g \left (x \right )+\left (\frac {d}{d x}\textit {\_Y} \left (x \right )\right ) f \left (x \right )+\frac {d^{3}}{d x^{3}}\textit {\_Y} \left (x \right )\right \}, \left \{\textit {\_Y} \left (x \right )\right \}\right )}{\mathit {DESol}\left (\left \{-\textit {\_Y} \left (x \right ) g \left (x \right )+\left (\frac {d}{d x}\textit {\_Y} \left (x \right )\right ) f \left (x \right )+\frac {d^{3}}{d x^{3}}\textit {\_Y} \left (x \right )\right \}, \left \{\textit {\_Y} \left (x \right )\right \}\right )}\right \}\]