\[ y'(x)=\frac {x \sqrt {4 a x-y(x)^2}+2 a}{y(x)} \] ✓ Mathematica : cpu = 1.22345 (sec), leaf count = 101
\[\left \{\left \{y(x)\to -\frac {\sqrt {-256 a^4 x^4+32 a^2 e^{c_1} x^2+4096 a^5 x-e^{2 c_1}}}{32 a^2}\right \},\left \{y(x)\to \frac {\sqrt {-256 a^4 x^4+32 a^2 e^{c_1} x^2+4096 a^5 x-e^{2 c_1}}}{32 a^2}\right \}\right \}\] ✓ Maple : cpu = 0.269 (sec), leaf count = 27
\[ \left \{ -\sqrt {- \left ( y \left ( x \right ) \right ) ^{2}+4\,ax}-{\frac {{x}^{2}}{2}}-{\it \_C1}=0 \right \} \]