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