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Definition

Common Ratio of a Geometric Sequence

The common ratio of a geometric sequence, denoted by rr, is the constant value obtained when any term is divided by the term immediately before it. Formally, r=anan1r = \frac{a_n}{a_{n-1}} for every integer n2n \geq 2. To verify that a sequence is geometric, compute the ratio between each pair of consecutive terms: if all ratios are the same value, that value is rr and the sequence is geometric. If even one ratio differs from the others, the sequence is not geometric and no common ratio exists. The common ratio can be any nonzero number — positive, negative, a whole number, or a fraction.

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Updated 2026-05-26

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Ch.12 Sequences, Series and Binomial Theorem - Intermediate Algebra @ OpenStax

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