Answer
$\text{Domain: }
(-\infty, \infty)
\\\text{Range: }
(-\infty,0)
\\\text{Horizontal Asymptote: }
y=0$
Work Step by Step
The black graph is the graph given in Figure 1, $y=
e^x
$.
The red graph is the graph of the given function, $
f(x)=-e^{-x}
$. It is the result of reflecting the black graph about the $y-$axis and about the $x-$axis.
The red graph has the following characteristics:
\begin{array}{l}\require{cancel}
\text{Domain: }
(-\infty, \infty)
\\\text{Range: }
(-\infty,0)
\\\text{Horizontal Asymptote: }
y=0
.\end{array}