\[ \left (x y'(x)-y(x)\right ) y''(x)-\left (y'(x)^2+1\right )^2=0 \] ✗ Mathematica : cpu = 1.55603 (sec), leaf count = 0 , could not solve
DSolve[-(1 + Derivative[1][y][x]^2)^2 + (-y[x] + x*Derivative[1][y][x])*Derivative[2][y][x] == 0, y[x], x]
✓ Maple : cpu = 0.443 (sec), leaf count = 66
\[ \left \{ y \left ( x \right ) ={\it RootOf} \left ( -\ln \left ( x \right ) +\int ^{{\it \_Z}}\!{\frac {-{\it \_f}+{\it RootOf} \left ( -{\it \_C1}\,\tan \left ( {{\it \_Z}}^{-1} \right ) {\it \_Z}+{\it \_f}\,{\it \_C1}\,\tan \left ( {{\it \_Z}}^{-1} \right ) +{\it \_C1}\,{\it \_Z}\,{\it \_f}+\tan \left ( {{\it \_Z}}^{-1} \right ) {\it \_Z}\,{\it \_f}+{\it \_C1}+\tan \left ( {{\it \_Z}}^{-1} \right ) +{\it \_Z}-{\it \_f} \right ) }{{{\it \_f}}^{2}+1}}{d{\it \_f}}+{\it \_C2} \right ) x \right \} \]