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Definition

Common Difference of an Arithmetic Sequence

The common difference of an arithmetic sequence, denoted by dd, is the constant value obtained when any term is subtracted from the term that directly follows it. Formally, d=anāˆ’anāˆ’1d = a_n - a_{n-1} for every integer n≄2n \geq 2. The common difference can be positive, negative, or zero. When d>0d > 0 the terms increase (e.g., 5,9,13,17,…5, 9, 13, 17, \dots has d=4d = 4); when d<0d < 0 the terms decrease (e.g., 10,3,āˆ’4,āˆ’11,…10, 3, -4, -11, \dots has d=āˆ’7d = -7); and when d=0d = 0 every term is identical. To verify that a sequence is arithmetic, compute the difference between each pair of consecutive terms: if all differences equal the same value, that value is dd.

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Updated 2026-05-25

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