\[ y(x) y''(x)+3 y(x) y'(x)-3 y'(x)^2-y(x)^2=0 \] ✓ Mathematica : cpu = 0.131868 (sec), leaf count = 25
DSolve[-y[x]^2 + 3*y[x]*Derivative[1][y][x] - 3*Derivative[1][y][x]^2 + y[x]*Derivative[2][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to \frac {c_2 e^x}{\sqrt {1-2 e^{x+c_1}}}\right \}\right \}\] ✓ Maple : cpu = 0.912 (sec), leaf count = 68
dsolve(diff(diff(y(x),x),x)*y(x)-3*diff(y(x),x)^2+3*y(x)*diff(y(x),x)-y(x)^2=0,y(x))
\[y \left (x \right ) = -\frac {\sqrt {2}\, \sqrt {\left ({\mathrm e}^{x} c_{1}-c_{2}\right ) {\mathrm e}^{2 x}}}{2 \,{\mathrm e}^{x} c_{1}-2 c_{2}}\]