\[ -18 y(x) y'(x) y''(x)+15 y'(x)^3+4 y(x)^2 y^{(3)}(x)=0 \] ✗ Mathematica : cpu = 0.0760898 (sec), leaf count = 0 , could not solve
DSolve[15*Derivative[1][y][x]^3 - 18*y[x]*Derivative[1][y][x]*Derivative[2][y][x] + 4*y[x]^2*Derivative[3][y][x] == 0, y[x], x]
✓ Maple : cpu = 0.738 (sec), leaf count = 22
\[ \left \{ y \left ( x \right ) ={\frac {{\it \_C3}}{ \left ( {{\it \_C2}}^{2}+2\,{\it \_C2}\,x+{x}^{2}-4\,{\it \_C1} \right ) ^{2}}} \right \} \]