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