\[
\boxed{
 \left( {\frac {{\it e1}\, \left( x+a \right) }{ \left(  \left( x+a \right) ^{2}+ \left( y \left( x \right)  \right) ^{2} \right) ^{3/2}}}+{\frac {{\it e2}\, \left( x-a \right) }{ \left(  \left( x-a \right) ^{2}+ \left( y \left( x \right)  \right) ^{2} \right) ^{3/2}}} \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -y \left( x \right)  \left( {\frac {{\it e1}}{ \left(  \left( x+a \right) ^{2}+ \left( y \left( x \right)  \right) ^{2} \right) ^{3/2}}}+{\frac {{\it e2}}{ \left(  \left( x-a \right) ^{2}+ \left( y \left( x \right)  \right) ^{2} \right) ^{3/2}}} \right) =0}
\]