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