Question

Which of the following are geometric sequences?

More than one answer will work.

A. 2, -2, 2, -2, 2, -2, 2
B. 1, 4, 9, 16, 25, 36, 49
C. 10, 5, 2.5, 1.25, 0.625, 0.3125
D. 1, 2, 4, 8, 16, 32

Answer 1

do you recall what defines a seq as geometric?

Answer 2

connected by a common #

Answer 3

given a seq: a,b,c,d

a geometric seq is defined if:

a*r = b
b*r = c where r is a common ration, or multiplier
c*r = d

Answer 4

as such:

d/c = c/b = b/a

Answer 5

lets look at A

A. 2, -2, 2, -2, 2, -2, 2 ; *-1 gives us each next value

Answer 6

2/-2 = -2/2 = 2/-1 = ....

Answer 7

I think C is one

Answer 8

lol, that -1 just kinda slipped in there on accident

Answer 9

yes, it looks like C is a /2 each time

Answer 10

I dont think A is one

Answer 11

why not?

Answer 12

because the # just changes from 2 to -2 it just doesnt make sense to me

Answer 13

2*r = -2 ; r=-1

-2*r = 2 ; r= -1

they have a common multiplier

Answer 14

ohhh i see so A is one

Answer 15

can you tell if D is one?

Answer 16

I think it one because each time it gets multiplied by 2

Answer 17

very good

Answer 18

what about B? is there any hope for it?

Answer 19

I dont think B is one because it doesnt look like it has any common #s

Answer 20

32/16=16/8=8/4=4/2=2/1=2????????

Answer 21

i agree

1*r = 4 ; r=4/1

4*r = 9 ; r= 9/4

since 4/1 not equal 9/4, there is no common value

Answer 22

ok thank you so much! :)

Answer 23

youre welcome