\varphi(x)=\frac{-1+2(u-x)}{(u-x)^2}=\frac{-1+2v}{v^2}=\frac{-1}{v^2}+\frac{2}{v}\\
\frac{1}{\mu}d\mu=\frac{-1}{v^2}dv+\frac{2}{v}dv\\