\[ \left (a+x^2+y(x)^2\right ) y'(x)+2 x y(x)=0 \] ✓ Mathematica : cpu = 0.0191656 (sec), leaf count = 297
\[\left \{\left \{y(x)\to \frac {\sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}{3 \sqrt [3]{2}}-\frac {3 \sqrt [3]{2} \left (a+x^2\right )}{\sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}\right \},\left \{y(x)\to \frac {3 \left (1+i \sqrt {3}\right ) \left (a+x^2\right )}{2^{2/3} \sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}-\frac {\left (1-i \sqrt {3}\right ) \sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}{6 \sqrt [3]{2}}\right \},\left \{y(x)\to \frac {3 \left (1-i \sqrt {3}\right ) \left (a+x^2\right )}{2^{2/3} \sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}-\frac {\left (1+i \sqrt {3}\right ) \sqrt [3]{\sqrt {2916 \left (a+x^2\right )^3+6561 c_1^2}+81 c_1}}{6 \sqrt [3]{2}}\right \}\right \}\]
✓ Maple : cpu = 0.022 (sec), leaf count = 470
\[ \left \{ y \left ( x \right ) ={\frac {1}{2}\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}-2\,{\frac {{x}^{2}+a}{\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}},y \left ( x \right ) =-{\frac {1}{4}\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}+{({x}^{2}+a){\frac {1}{\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}}}-{\frac {i}{2}}\sqrt {3} \left ( {\frac {1}{2}\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}+2\,{\frac {{x}^{2}+a}{\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}} \right ) ,y \left ( x \right ) =-{\frac {1}{4}\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}+{({x}^{2}+a){\frac {1}{\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}}}+{\frac {i}{2}}\sqrt {3} \left ( {\frac {1}{2}\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}+2\,{\frac {{x}^{2}+a}{\sqrt [3]{-12\,{\it \_C1}+4\,\sqrt {4\,{x}^{6}+12\,a{x}^{4}+12\,{a}^{2}{x}^{2}+4\,{a}^{3}+9\,{{\it \_C1}}^{2}}}}} \right ) \right \} \]