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Geometric sequences

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404
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+117

Using the graph below, what are the common ratio and the general term equation, an, of the geometric sequence?

Hint: an = a1(r)n − 1, where a1 is the first term and r is the common ratio

failurewithasmile  Apr 14, 2017
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#1
+17693
+3

a1 = -24, a2 = -8, a3 = -8/3, ...

To go from a1 to a2, divide by 3, or multiply by 1/3; thus the common ratio is 1/3.

To find a0, multiply a1 by 3 (because you are going backwards) to get -72.

The formula for the nth term is :  an  =  a0·rn     --->     an  =  72 · (1/3)n.

geno3141  Apr 14, 2017
#2
+117
+1

Is it r=1/3, an=-24(1/3)^n-1

failurewithasmile  Apr 14, 2017
#3
+117
+1

Hi @CPhill, thanks for all of your help. I was wondering if the answer to this question is Is it r=1/3, an=-24(1/3)^n-1?

failurewithasmile  Apr 15, 2017
#4
+79894
+1

Yep...geno is correct

Check :

-24(1/3)^(n - 1)    for terms 1, 2, 3  = -24, -8, -8/3 = -2. 6....

CPhill  Apr 15, 2017

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