1.
Define f:R→Rf:\mathbb R\to\mathbb R by f(x)={(x−a)e1x−a−1e1x−a+1x≠a0x=af(x)=\begin{cases}(x-a)\frac{e^{\frac1{x-a}}-1}{e^{\frac1{x-a}}+1}&x\neq a\\0&x=a\end{cases}. Then which is true?