[问答题]
The function f is
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+rzg;zu(jba,) 5;ozs; kr ob zefined by $f(x)=e^{2 x}-4 e^{x}+2$ , for $x \in \mathbb{R}, x \leq a$ , where $a \in \mathbb{R}$ . Part of the graph of y=f(x) is shown in the following diagram.
1. Find the largest value of a such that f has an inverse function.
2. For this value of a , find an expression for $ f^{-1}(x)$ , stating its domain.
