To classify the sequence \( 9, 4, -1, -6, \ldots \):
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Arithmetic sequence: A sequence is arithmetic if there is a constant difference between consecutive terms. For this sequence:
- \( 4 - 9 = -5 \)
- \( -1 - 4 = -5 \)
- \( -6 - (-1) = -5 \)
Since the difference is consistent at \(-5\), this is an arithmetic sequence.
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Geometric sequence: A sequence is geometric if there is a constant ratio between consecutive terms. In this case:
- \( \frac{4}{9}, \frac{-1}{4}, \frac{-6}{-1} \) are not constant ratios.
Therefore, the correct classification is:
arithmetic sequence.