5.5 The Substitution Rule/69

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

$u=e^{z}+zdu=e^{z}+1$