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

goformit100 · Answer

B. an = -2 + an-1

blockcolder · Answer

It's geometric, so there's gotta be some multiplication involved.

anonymous · Answer

I'm pretty sure it is D.  If you take a2 divided by a1, and a3 divided by a2, you get a common ration of -4 for each.  And since it is geometric, we are multiplying between each (so that rules out option A, I think).