\[ y(x) y''(x)+3 y(x) y'(x)-3 y'(x)^2-y(x)^2=0 \] ✓ Mathematica : cpu = 0.0688579 (sec), leaf count = 25
\[\left \{\left \{y(x)\to \frac {c_2 e^x}{\sqrt {1-2 e^{c_1+x}}}\right \}\right \}\]
✓ Maple : cpu = 0.063 (sec), leaf count = 68
\[ \left \{ y \left ( x \right ) ={\frac {1}{2\,{{\rm e}^{-x}}{\it \_C1}-2\,{\it \_C2}}\sqrt {-2\, \left ( {{\rm e}^{-x}}{\it \_C1}-{\it \_C2} \right ) {{\rm e}^{x}}}},y \left ( x \right ) =-{\frac {1}{2\,{{\rm e}^{-x}}{\it \_C1}-2\,{\it \_C2}}\sqrt {-2\, \left ( {{\rm e}^{-x}}{\it \_C1}-{\it \_C2} \right ) {{\rm e}^{x}}}} \right \} \]