eπ1−x\frac{e^{\pi}}{1-x}1−xeπ
x1−ex\frac{x}{1-e^{x}}1−exx
exx−1\frac{e^{x}}{x-1}x−1ex
ex(x−1)2\frac{e^{x}}{(x-1)^{2}}(x−1)2ex