Answer
It is a geometric sequence.
$r=3$
Work Step by Step
A sequence is geometric if $\frac{a_2}{a_1}=\frac{a_3}{a_2}=\frac{a_4}{a_3}=...=r$
For the given sequence we have that:
$\frac{a_2}{a_1}=\frac{6}{2}=3$
$\frac{a_3}{a_2}=\frac{18}{6}=3$
$\frac{a_4}{a_3}=\frac{54}{18}=3$
$\frac{a_5}{a_4}=\frac{162}{54}=3$
It is a geometric sequence.
Common ratio: $r=3$
