\[ \boxed { \left ( -{a}^{2}+{x}^{2} \right ) \left ( {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) \right ) ^{2}+2\,xy \left ( x \right ) {\frac {\rm d}{{\rm d}x}}y \left ( x \right ) + \left ( y \left ( x \right ) \right ) ^{2}=0} \]
Mathematica: cpu = 0.010001 (sec), leaf count = 27 \[ \left \{\left \{y(x)\to \frac {c_1}{a-x}\right \},\left \{y(x)\to \frac {c_1}{a+x}\right \}\right \} \]
Maple: cpu = 0.0 (sec), leaf count = 23 \[ \left \{ y \left ( x \right ) ={\frac {{\it \_C1}}{a-x}},y \left ( x \right ) ={\frac {{\it \_C1}}{x+a}} \right \} \]