\[ a \left (x y'(x)-y(x)\right )^2-b+x y''(x)=0 \] ✓ Mathematica : cpu = 6.63036 (sec), leaf count = 51
\[\left \{\left \{y(x)\to x \left (\int _1^x\frac {\sqrt {-\frac {b}{a}} \tan \left (c_1-a \sqrt {-\frac {b}{a}} K[2]\right )}{K[2]^2}dK[2]+c_2\right )\right \}\right \}\] ✓ Maple : cpu = 2.748 (sec), leaf count = 35
\[ \left \{ y \left ( x \right ) = \left ( \int \!{\frac {i}{{x}^{2}}\tan \left ( -i\sqrt {a}\sqrt {b}x+{\it \_C1} \right ) \sqrt {b}{\frac {1}{\sqrt {a}}}}\,{\rm d}x+{\it \_C2} \right ) x \right \} \]