Answer
See graph.
domain $(-\infty,\infty)$, range $(-\infty,0)$, H.A. $y=0$.
Work Step by Step
Step 1. To obtain the graph of $f(x)=-e^{x}$ from $y=e^x$, reflect the curve across the x-axis. See graph.
Step 2. We can determine the domain $(-\infty,\infty)$, range $(-\infty,0)$, horizontal asymptote H.A. $y=0$.