Which formula could be used to find the n th term for the geometric sequence 2,6,18,54 ?

The sequence has first term 2 and common ratio 3, since each term is multiplied by 3. A geometric sequence with first term a₁ and common ratio r has nth term aₙ = a₁ × r^(n−1), so here aₙ = 2 × 3^(n−1). This is choice C.

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