{{{ THE BOLDED CHARACTERS SHOULD BE SMALL. }}}
SEQUENCE: 6, 18, 54, 162
18/6 = 3
54/18 = 3
162/54 = 3
then, r (common ratio) = 3
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RECURSIVE RULE: r = 3
an = a(n - 1) × r [formula]
ANSWER: an = a(n - 1) × 3
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ITERIATIVE RULE: r = 3, a1 = 6
an = a1 × r^(n - 1) [formula] [ ^(n-1) is an exponent]
ANSWER: an = 6 × 3^(n - 1)