Question

Three terms of a geometric sequence are shown.

f(1) = 1, f(3) = 9, f(6) = –243

Which recursive formula could define the sequence?

a. f(n + 1) = 9f(n)
b. f(n + 1) = –9f(n)
c. f(n + 1) = 3f(n)
d. f(n + 1) = –3f(n)

Need Help! Don't Give Answer

Answer 1

@ganeshie8

Answer 2

Have you considered calculating the first 6 terms of each?

a. f(n + 1) = 9f(n)

f(1) = 1
f(2) = 9f(1) = 9(1) = 9
f(3) = 9f(2) = 9(9) = 81 -- Well, that's no good. We were hoping for 9.

You do the rest.

Answer 3

@justsmile531 are you set?

What part do you have trouble with?

Answer 4

@tkhunny Can you explain how you did that?

Answer 5

can you tell me in your own words what a geometric sequence is?

Answer 6

I used the "a" formula definition, starting with n = 1.

Answer 7

Can you explain step by step @tkhunny

Answer 8

I did already.

'a' formula definition.

a. f(n + 1) = 9f(n)

n = 1

f(1+1) = 9f(1)
f(2) = 9f(1)

We are given f(1)

f(2) = 9(1) = 9

Now, we know f(2).

Use this to find f(3) by substituting n = 2.

etc.

Answer 9

So A is not the answer; Correct ? @tkhunny

Answer 10

Can you dummy it down please? @PaxPolaris

Answer 11

a Geometric sequence is when you keep multiplying the same number (the common ratio) ... to get the next number in the sequence. correct?

Answer 12

Is it C

Answer 13

if you keep multiplying 3 .... you will never get a negative number in your sequence.... (it can't have -243)

Answer 14

So D

Answer 15

1, ___, 9, ___, ___, -243

Answer 16

correct

Answer 17

Thank you

Answer 18

1, -3 , 9, -27, 81, -243...