Question

4 of 84 of 8 Items


Question
Find the recursive formula for the geometric sequence −19, −13, −1, −3, −9,...
(1 point)
a1 =

, an=
an−1

Answer 1

The list as written is not a geometric sequence: the ratios between consecutive terms are
-13/−19 = 13/19, −1/−13 = 1/13, −3/−1 = 3, −9/−3 = 3,
so the ratio is not constant for the whole list.

Do you mean the geometric tail −1, −3, −9, …? If so the recursive formula for that subsequence (with its first term −1) is
a1 = −1, an = 3·a(n−1) for n ≥ 2.

If you intended a different sequence, please confirm the correct terms (or whether one of the signs/numbers is a typo) and I’ll give the recursive formula.