\[
\boxed{
 \left(  \left( y \left( x \right)  \right) ^{2}+ \left( 1-a \right) {x}^{2} \right)  \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) ^{2}+2\,axy \left( x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) + \left( 1-a \right)  \left( y \left( x \right)  \right) ^{2}+{x}^{2}=0}
\]