\[ a \left (-\sqrt {y(x)}\right )-b x+y'(x)=0 \] ✗ Mathematica : cpu = 301.207 (sec), leaf count = 0 , timed out
$Aborted
✓ Maple : cpu = 0.071 (sec), leaf count = 68
\[ \left \{ -{\frac {1}{2}\ln \left ( \sqrt {y \left ( x \right ) }ax+b{x}^{2}-2\,y \left ( x \right ) \right ) }+{a\sqrt {y \left ( x \right ) }{\it Artanh} \left ( {1 \left ( a\sqrt {y \left ( x \right ) }+2\,bx \right ) {\frac {1}{\sqrt {y \left ( x \right ) \left ( {a}^{2}+8\,b \right ) }}}} \right ) {\frac {1}{\sqrt {y \left ( x \right ) \left ( {a}^{2}+8\,b \right ) }}}}+{\it \_C1}=0 \right \} \]