Answer
$\frac{1}{4x}$
Work Step by Step
We are given the expression $(4x)^{-1}$
$(4x)^{-1}=\frac{1}{4x}$
In general, $a^{-n}=\frac{1}{a^{n}}$ (where a is a nonzero real number and n is a positive integer).
Since the 4 and the x are in parentheses, both are evaluated by the exponent.