\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) =- \left( {\frac {{\it Ei} \left( 1,-\ln  \left( -1+y \left( x \right)  \right)  \right) }{x}}-{\it \_F1} \left( x \right)  \right) \ln  \left( -1+y \left( x \right)  \right) =0}
\]