\[
\boxed{
 \left(  \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) ^{2}+1 \right)  \left( \arctan \left( {\frac {\rm d}{{\rm d}x}}y \left( x \right)  \right) +ax \right) +{\frac {\rm d}{{\rm d}x}}y \left( x \right) =0}
\]