Which best describes the relationship between the successive terms in the sequence shown?9, –1, –11, –21, …

Subtract each term from the next: –1 − 9 = –10, –11 − (–1) = –10, and –21 − (–11) = –10. Since the difference is constant, the sequence is arithmetic, and its common difference is –10. Choice A, “The common difference is –10,” is correct.

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