\[ y'(x)=\frac {1}{512} x \left (24 a^2 x^8 y(x)+a^3 x^{12}+8 a^2 x^8+192 a x^4 y(x)^2+128 a x^4 y(x)-256 a x^2+512 y(x)^3+512 y(x)^2+512\right ) \] ✓ Mathematica : cpu = 0.216223 (sec), leaf count = 101
\[\text {Solve}\left [-\frac {29}{3} \text {RootSum}\left [-29 \text {$\#$1}^3+3 \sqrt [3]{29} \text {$\#$1}-29\& ,\frac {\log \left (\frac {\frac {1}{8} \left (3 a x^5+8 x\right )+3 x y(x)}{\sqrt [3]{29} \sqrt [3]{x^3}}-\text {$\#$1}\right )}{\sqrt [3]{29}-29 \text {$\#$1}^2}\& \right ]=\frac {1}{18} 29^{2/3} \left (x^3\right )^{2/3}+c_1,y(x)\right ]\] ✓ Maple : cpu = 0.158 (sec), leaf count = 40
\[ \left \{ y \left ( x \right ) =-{\frac {a{x}^{4}}{8}}-{\frac {1}{3}}+{\frac {29\,{\it RootOf} \left ( {x}^{2}-162\,\int ^{{\it \_Z}}\! \left ( 841\,{{\it \_a}}^{3}-27\,{\it \_a}+27 \right ) ^{-1}{d{\it \_a}}+6\,{\it \_C1} \right ) }{9}} \right \} \]