Answer
True.
Work Step by Step
Rewriting the function $h(x)$ as:
$$y=e^{-x}$$
Exchange $y$ with $-x$ and $x$ with $-y$:
$$-x=e^{-(-y)}$$ $$-x=e^y$$ $$\ln (-x)=\ln (e^y)$$ $$\ln (-x)=y\ln e$$ $$\ln (-x)=y$$ $$y=\ln (-x)$$
Replace $y$ with $f(x)$:
$$f(x)=\ln (-x)$$
Thus, the graph of $f(x)=\ln (-x)$ is a reflection of the graph of $h(x)=e^{-x}$ in the line $y=-x$.
