Question

Which of the following sequences are geometric?

Answer 1

Answer:

A and D

Step-by-step explanation:

the other guy explained it well

Answer 2

Let's start by first remembering what a "geometric sequence" is. A geometric sequence is a sequence of numbers that multiply by the same number each time. For example,
2, 4, 8, 16
is a geometric sequence since each number is multiplied by 2 from one to the next, but
2, 4, 6, 8 
is NOT a geometric sequence. We are adding 2 each time, but not multiplying, so it doesn't count. We have to be multiplying to have a geometric sequence.

[A] Let's look at A, are we multiplying by the same thing? 
6*3 = 18
18*3 = 54
54*3 = 162
162*3 = 486
Yes! We are multiplying by 3 each time. This is a geometric sequence!

[B] Are we multiplying by the same thing?
2*3/2 = 3
3*3/2 = 9/2 which is not 5.
NOPE

[C] Are we multiplying by the same thing?
2*5/2 = 5
5*5/2 = 25/2 which is not 8
NOPE

[D] Are we multiplying by the same thing?
-4*1/2 = -2
-2*1/2 = -1
-1*1/2 = -0.5
-0.5*1/2 = -0.25
-0.25*1/2 = -0.125
Yep, we are multiplying by 1/2 each time! This is a geometric sequence!