#### Answer

$g(x)=-2x+4$

#### Work Step by Step

Recall:
(1) The graph of $y=f(-x)$ involves a reflection about the $y$-axis of the parent function $f(x)$.
(2) The graph of $y=-f(x)$ involves a reflection about the $x$-axis of the parent function $f(x)$.
Thus, when $f(x)=2x-4$ is reflected about the $x$-axis, the equation of the new function $g(x)$, is:
\begin{align*}
g(x)&=-f(x)\\
g(x)&=-(2x-4)\\
g(x)&=-2x+4
\end{align*}