\[ \boxed { {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) =1/2\,{\frac {1+2\,\sqrt {4\,{x}^{2}y \left ( x \right ) +1}{x}^{4}}{{x}^{3}}}=0} \]
Mathematica: cpu = 0.177022 (sec), leaf count = 35 \[ \left \{\left \{y(x)\to \frac {-24 c_1 x^5+36 c_1^2 x^2+4 x^8-9}{36 x^2}\right \}\right \} \]
Maple: cpu = 0.172 (sec), leaf count = 26 \[ \left \{ {\it \_C1}-{\frac {1}{x}\sqrt {4\,{x}^{2}y \left ( x \right ) + 1}}+{\frac {2\,{x}^{3}}{3}}=0 \right \} \]