To classify the sequence \(9, 4, -1, -6, \ldots\), we will check the differences between consecutive terms.
- The difference between the first two terms: \(4 - 9 = -5\)
- The difference between the second and third terms: \(-1 - 4 = -5\)
- The difference between the third and fourth terms: \(-6 - (-1) = -5\)
Since the difference between each pair of consecutive terms is constant (equal to \(-5\)), this sequence is classified as an arithmetic sequence.
So, the correct response is:
arithmetic sequence.