5.5 The Substitution Rule/69

${\begin{aligned}\int _{0}^{1}\left({\frac {e^{z}+1}{e^{z}+z}}\right)&=\int _{}^{}\left((e^{z}+1)({\frac {1}{e^{z}+z}})\right)u=e^{z}+zdu=e^{z}+1\end{aligned}}$