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