\[
\boxed{
{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) =-{\frac { \left( \phi \left( {x}^{3} \right) -\phi \left( x \right) {\frac {\rm d}{{\rm d}x}}\phi \left( x \right) -{\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}\phi \left( x \right)  \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) }{{\frac {\rm d}{{\rm d}x}}\phi \left( x \right) + \left( \phi \left( x \right)  \right) ^{2}}}-{\frac { \left(  \left( {\frac {\rm d}{{\rm d}x}}\phi \left( x \right)  \right) ^{2}- \left( \phi \left( x \right)  \right) ^{2}{\frac {\rm d}{{\rm d}x}}\phi \left( x \right) -\phi \left( x \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}\phi \left( x \right)  \right) y \left( x \right) }{{\frac {\rm d}{{\rm d}x}}\phi \left( x \right) + \left( \phi \left( x \right)  \right) ^{2}}}=0}
\]