Answer :

To find [tex]\( f(x) \)[/tex] when [tex]\( x = -1 \)[/tex] for the given function [tex]\( f(x) = 4^x \)[/tex]:

1. Substitute [tex]\( x = -1 \)[/tex] into the function:
[tex]\[ f(-1) = 4^{-1} \][/tex]

2. Evaluate [tex]\( 4^{-1} \)[/tex]:
[tex]\[ 4^{-1} = \frac{1}{4} = 0.25 \][/tex]

3. Round the result to the nearest thousandth:
Since [tex]\( 0.25 \)[/tex] already has fewer than three decimal places, it remains [tex]\( 0.25 \)[/tex].

Therefore, the value of [tex]\( f(x) \)[/tex] when [tex]\( x = -1 \)[/tex] is [tex]\( 0.25 \)[/tex], and rounding to the nearest thousandth still gives [tex]\( 0.25 \)[/tex].