\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) ={\frac {-125+300\,x-240\,{x}^{2}+64\,{x}^{3}-80\, \left( y \left( x \right)  \right) ^{2}+64\,x \left( y \left( x \right)  \right) ^{2}+64\, \left( y \left( x \right)  \right) ^{3}}{ \left( 4\,x-5 \right) ^{3}}}=0}
\]