Question

Find the recursive formula for the arithmetic sequence 7, 5, 3, 1, −1
, . . .(1 point)

a1=7
, an=−2an−1


a1=7
, an=an−1+2


a1=7
, an=an−1−2


a1=7
, an=2an−1

Answer 1

a1 = 7, an = a_{n-1} − 2 for n ≥ 2.

Each term decreases by 2 (7 → 5 → 3 → 1 → −1), so the recursive step is subtract 2.