\[
\boxed{
3\, \left( {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right)  \right) {\it d4y} \left( x \right) -5\, \left( {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right)  \right) ^{2}=0}
\]