\[ y'(x)=\frac {x^3 \sqrt {4 a x-y(x)^2}+x^2 \sqrt {4 a x-y(x)^2}+\sqrt {4 a x-y(x)^2}+2 a}{y(x)} \] ✓ Mathematica : cpu = 2.94089 (sec), leaf count = 145
\[\left \{\left \{y(x)\to -\frac {1}{12} \sqrt {576 a x-9 x^8-24 x^7-16 x^6-72 x^5-96 x^4-144 x^2-72 c_1 x^4-96 c_1 x^3-288 c_1 x-144 c_1{}^2}\right \},\left \{y(x)\to \frac {1}{12} \sqrt {576 a x-9 x^8-24 x^7-16 x^6-72 x^5-96 x^4-144 x^2-72 c_1 x^4-96 c_1 x^3-288 c_1 x-144 c_1{}^2}\right \}\right \}\] ✓ Maple : cpu = 0.35 (sec), leaf count = 35
\[ \left \{ -\sqrt {- \left ( y \left ( x \right ) \right ) ^{2}+4\,ax}-{\frac {{x}^{4}}{4}}-{\frac {{x}^{3}}{3}}-x-{\it \_C1}=0 \right \} \]