Write the recursive formula for the geometric sequence.

a1 = -2 a2 = 8 a3 = -32

A. an = -4 + an-1

B. an = -2 + an-1

C. an = -2 • an-1

D. an = -4 • an-1

Question

Write the recursive formula for the geometric sequence.

a1 = -2  a2 = 8  a3 = -32

A. an = -4 + an-1

B. an = -2 + an-1

C. an = -2 • an-1

D. an = -4 • an-1

anonymous · Answer

To start, you know that it must be geometric, meaning that the answer can't be A or B. Second, a3/a2 = a2/a1 = -4. Since the ratio between one to the next is -4, you know it can't be C, so the answer is D

D.