\[ \left (y(x)^2-a^2 x^2\right ) y'(x)^2+\left (1-a^2\right ) x^2+2 x y(x) y'(x)=0 \] ✓ Mathematica : cpu = 0.116077 (sec), leaf count = 49
\[\left \{\left \{y(x)\to a c_1-\sqrt {-x^2+c_1{}^2}\right \},\left \{y(x)\to a c_1+\sqrt {-x^2+c_1{}^2}\right \}\right \}\] ✓ Maple : cpu = 0.199 (sec), leaf count = 161
\[y \relax (x ) = \sqrt {a^{2}-1}\, x\]