How many terms are in the finite arithmetic sequence 5, -2, -9, ..., -65?

1. Find the common difference: -2 - 5 = -7. 2. Write the general term: a_n = 5 + (n - 1)(-7) = 12 - 7n. 3. Set the last term equal to -65: 12 - 7n = -65. 4. Solve: 7n = 77, so n = 11, and the sequence has 11 terms. 5. Option A, 10 terms, comes from solving 5 - 7n = -65, which forgets that the first term uses n = 1, not n = 0. _Source: OpenStax Algebra and Trigonometry (CC BY 4.0), Ch 13 "Sequences, Probability and Counting Theory", section 13.2 ARITHMETIC SEQUENCES_