Question

Which best describes the relationship between the successive terms in the sequence shown?

9, –1, –11, –21, …

The common difference is –10.
The common difference is 10.
The common ratio is –9.
The common ratio is 9.

Answer 1

The common difference is −10.

Each successive term is 10 less than the previous: −1−9 = −10, −11−(−1) = −10, −21−(−11) = −10, so it's an arithmetic sequence with difference −10.