To represent the geometric sequence given as 6, 18, 54, ..., we first need to identify the first term and the common ratio.
- The first term \( a = 6 \).
- The common ratio \( r = \frac{18}{6} = 3 \).
The general formula for the nth term of a geometric sequence is given by:
\[ f(n) = a \cdot r^{(n-1)} \]
Substituting the values we have:
\[ f(n) = 6 \cdot 3^{(n-1)} \]
This means that the correct function representing the geometric sequence is:
\[ f(x) = 6(3)^{x-1} \]
So the correct response is:
f(x) = 6(3)^{x-1}