Question

how do i use the geometric sequence formula to figure out what the 6th term is (after 7)?
15,13,11,9,7 ?

Answer 1

(15-n)=13
what is n

Answer 2

so you take 7-2=5
the 6th term is 5

Answer 3

yes, but i need to use the geometric sequence formula

Answer 4

\[a_n=a_1r ^{n-1}\]

Answer 5

an=15*2^(n-1)

Answer 6

does this help or not?
@andreadesirepen

Answer 7

n-1 would be 5?

Answer 8

wouldnt the r be 1.2?

Answer 9

Hmm... sorry to contradict, but this doesn't look like a geometric sequence at all, it looks like an aritmetic sequence.

Answer 10

geometric sequences are the result of multiplying (but there's nothing being constantly multiplied here).

Answer 11

this is what im being asked:
What is the height of each ball on the fifth bounce (i.e., Height 6)? Use the geometric sequence formula

Answer 12

i dropped the ball from 15ft high, and the first time it bounced 13ft ft then 11 then 9 etc...

Answer 13

@jtvatsim

Answer 14

hmm.. it just doesn't make sense because your ratio is changing every time, so you can't write a typical geometric sequence...

Answer 15

your ratio starts as 13/15 = 0.867
Then changes to 11/13 = 0.846.
Then changes again to 9/11 = 0.818.

If the ratio isn't constant, I'm not sure that it's possible to even use a geometric sequence.

Answer 16

what if i round if off and leave it at just 8?

Answer 17

*.8

Answer 18

perhaps, that would be an approximation, so I hope an exact answer isn't needed. -.-

Answer 19

i thought it had to be 15/ 13 though

Answer 20

I'm pretty sure that it has to be 13/15 because your values are getting smaller over time.

Answer 21

If they were growing then 15/13 would make sense.

Answer 22

oh ok. so i would use this equation, 15*(.8)^5 ?

Answer 23

yes