\[ a^2 \left (-x^2\right )-2 a^2 x y(x) y'(x)+\left (1-a^2\right ) y(x)^2 y'(x)^2+y(x)^2=0 \] ✓ Mathematica : cpu = 0.286948 (sec), leaf count = 148
\[\left \{\left \{y(x)\to -\frac {\sqrt {e^{-2 c_1} \left (\left (a^2-1\right )^3 \left (-e^{2 c_1}\right ) x^2+2 \left (a^2-1\right ) x e^{\left (a^2+1\right ) c_1}+e^{2 a^2 c_1}\right )}}{\sqrt {\left (a^2-1\right )^3}}\right \},\left \{y(x)\to \frac {\sqrt {e^{-2 c_1} \left (\left (a^2-1\right )^3 \left (-e^{2 c_1}\right ) x^2+2 \left (a^2-1\right ) x e^{\left (a^2+1\right ) c_1}+e^{2 a^2 c_1}\right )}}{\sqrt {\left (a^2-1\right )^3}}\right \}\right \}\]
✓ Maple : cpu = 0.19 (sec), leaf count = 189
\[ \left \{ y \left ( x \right ) ={\it RootOf} \left ( -\ln \left ( x \right ) +\int ^{{\it \_Z}}\!{\frac {{\it \_a}}{ \left ( {{\it \_a}}^{2}+1 \right ) \left ( {{\it \_a}}^{2}{a}^{2}-{{\it \_a}}^{2}+{a}^{2} \right ) } \left ( -{{\it \_a}}^{2}{a}^{2}+{{\it \_a}}^{2}-{a}^{2}+\sqrt {{{\it \_a}}^{2}{a}^{2}-{{\it \_a}}^{2}+{a}^{2}} \right ) }{d{\it \_a}}+{\it \_C1} \right ) x,y \left ( x \right ) ={\it RootOf} \left ( -\ln \left ( x \right ) -\int ^{{\it \_Z}}\!{\frac {{\it \_a}}{ \left ( {{\it \_a}}^{2}+1 \right ) \left ( {{\it \_a}}^{2}{a}^{2}-{{\it \_a}}^{2}+{a}^{2} \right ) } \left ( {{\it \_a}}^{2}{a}^{2}-{{\it \_a}}^{2}+{a}^{2}+\sqrt {{{\it \_a}}^{2}{a}^{2}-{{\it \_a}}^{2}+{a}^{2}} \right ) }{d{\it \_a}}+{\it \_C1} \right ) x,y \left ( x \right ) ={ax{\frac {1}{\sqrt {-{a}^{2}+1}}}},y \left ( x \right ) =-{ax{\frac {1}{\sqrt {-{a}^{2}+1}}}} \right \} \]