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What is the sum of the geometric sequence -4, 24, -144 . . . if there are 6 terms?
-159,963
26,660
26,661
159,963

- anonymous

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- anonymous

do 144 times neg 6 and that times neg 6 and that again times neg 6 to get all 6 terms

- anonymous

then add them

- anonymous

I did and the answer I got isn't the same as the options

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## More answers

- xapproachesinfinity

you mean the sum of geometric series not sequence?

- anonymous

No it says sequence

- xapproachesinfinity

first you need to find all the 6 terms then sum up

- xapproachesinfinity

you have three terms
so you are missing three more to make 6 terms

- xapproachesinfinity

what is the fourth term?

- anonymous

864, -5184, 31104 thee are the next three terms. At least that's what I got. If I add them up I don't get one of the answers they provide

- xapproachesinfinity

hmm really then you must of made a mistake

- xapproachesinfinity

how did you get the fourth term for example

- anonymous

\[-144 \times -6 = 864\]

- xapproachesinfinity

yes!

- xapproachesinfinity

you should get the right answer
i don't where you missed

- xapproachesinfinity

let's try doing the fomula
\[S_n=\frac{a(1-r^n)}{(1-r)}\]

- xapproachesinfinity

a=first term
n=6
r=-6

- xapproachesinfinity

@Tarynrachelle where you going?

- anonymous

I'm still here I'm doing the problem

- xapproachesinfinity

well low and behold i get one of the answer choices

- xapproachesinfinity

you should get the right answer once you do the calculations

- anonymous

The third answer?

- xapproachesinfinity

and actually i get the correct answer even the method i told you in the start
without formula. all of them should work since the formula came from it to begin with

- xapproachesinfinity

no

- anonymous

Idk what I'm doing wrong then.

- xapproachesinfinity

well to me they all give the same answer, something must be wrong in yur work

- xapproachesinfinity

anyway you got the formula, you got the other way
just see where you had missed things

- xapproachesinfinity

did you do it yet?

- xapproachesinfinity

use the formula

- anonymous

Okay well this is what I plug into the formula\[S _{n}=\frac{ 4(1-(-6)^{6}) }{ (1-(-6)) }\] am I wrong?

- xapproachesinfinity

yeah

- anonymous

That's supposed to be a -4

- xapproachesinfinity

yes -4 not 4 just about to say that

- anonymous

Is it still wrong even with the -4? Or is it correct with the -4?

- xapproachesinfinity

it is correct with -4

- anonymous

Okay. Hold on I think I see where I messed up

- anonymous

Nope still not getting one of the answer choices..

- anonymous

I plug it into my calculator and get 186614. That's the same answer I get when I add them all up

- anonymous

Could you explain the steps for me so I know what I'm doing wrong?

- xapproachesinfinity

hold a sec

- xapproachesinfinity

ok back

- xapproachesinfinity

how did you put it in your calc?

- anonymous

\[-4(1-(6)^6)\div(1-(6))\]

- xapproachesinfinity

no bottom
is (1-(-6))=1+6

- xapproachesinfinity

where are the negatives of 6?

- anonymous

My calculator wasn't getting the right answer but this is it
http://www.wolframalpha.com/input/?i=-4%281-%28-6%29%5E6%29%2F%281-%28-6%29%29

- xapproachesinfinity

well for the top you didn;t have to worry a lot of that negative
since you have an even power
but bottom no

- anonymous

It's the second choice

- xapproachesinfinity

yes!

- xapproachesinfinity

i think you put the wrong format into your calc

- anonymous

Probably. But thank you

- xapproachesinfinity

No problem

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