\[ a+x^4 \left (y'(x)+y(x)^2\right )=0 \] ✓ Mathematica : cpu = 0.097367 (sec), leaf count = 347
DSolve[a + x^4*(y[x]^2 + Derivative[1][y][x]) == 0,y[x],x]
\[\left \{\left \{y(x)\to -\frac {\frac {i \sqrt {\frac {2}{\pi }} c_1 \sinh \left (\frac {\sqrt {-a}}{x}\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}+\frac {i \sqrt {-a} \left (-\frac {2 \sqrt {\frac {2}{\pi }} \left (i \sinh \left (\frac {\sqrt {-a}}{x}\right )+\frac {i \sqrt {-a} x \cosh \left (\frac {\sqrt {-a}}{x}\right )}{a}\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}-\frac {\sqrt {\frac {2}{\pi }} c_1 \cosh \left (\frac {\sqrt {-a}}{x}\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}+\frac {\sqrt {\frac {2}{\pi }} c_1 \left (-\frac {\sqrt {-a} x \sinh \left (\frac {\sqrt {-a}}{x}\right )}{a}-\cosh \left (\frac {\sqrt {-a}}{x}\right )\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}\right )}{x}}{2 x \left (\frac {\sqrt {\frac {2}{\pi }} \cosh \left (\frac {\sqrt {-a}}{x}\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}-\frac {i \sqrt {\frac {2}{\pi }} c_1 \sinh \left (\frac {\sqrt {-a}}{x}\right )}{\sqrt {-\frac {i \sqrt {-a}}{x}}}\right )}\right \}\right \}\] ✓ Maple : cpu = 0.108 (sec), leaf count = 28
dsolve(x^4*(diff(y(x),x)+y(x)^2)+a = 0,y(x))
\[y \left (x \right ) = \frac {-\sqrt {a}\, \tan \left (\frac {\sqrt {a}\, \left (c_{1} x -1\right )}{x}\right )+x}{x^{2}}\]