Select the explicit formula for the sequence that correspond to this geometric series: 6 + 18 + 54 + 162 + 486

The first term is 6, and each term is 3 times the previous one, so the common ratio is 3. A geometric sequence has explicit formula aₖ = a₁r^(k−1), which here gives aₖ = 6 · 3^(k−1). This matches choice A.

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