Question

Will medal and fan
What is the sum of the geometric sequence -4, 24, -144 . . . if there are 6 terms?

-159,963
26,660
26,661
159,963

Answer 1

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

Answer 2

then add them

Answer 3

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

Answer 4

you mean the sum of geometric series not sequence?

Answer 5

No it says sequence

Answer 6

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

Answer 7

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

Answer 8

what is the fourth term?

Answer 9

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

Answer 10

hmm really then you must of made a mistake

Answer 11

how did you get the fourth term for example

Answer 12

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

Answer 13

yes!

Answer 14

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

Answer 15

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

Answer 16

a=first term
n=6
r=-6

Answer 17

@Tarynrachelle where you going?

Answer 18

I'm still here I'm doing the problem

Answer 19

well low and behold i get one of the answer choices

Answer 20

you should get the right answer once you do the calculations

Answer 21

The third answer?

Answer 22

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

Answer 23

no

Answer 24

Idk what I'm doing wrong then.

Answer 25

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

Answer 26

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

Answer 27

did you do it yet?

Answer 28

use the formula

Answer 29

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

Answer 30

yeah

Answer 31

That's supposed to be a -4

Answer 32

yes -4 not 4 just about to say that

Answer 33

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

Answer 34

it is correct with -4

Answer 35

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

Answer 36

Nope still not getting one of the answer choices..

Answer 37

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

Answer 38

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

Answer 39

hold a sec

Answer 40

ok back

Answer 41

how did you put it in your calc?

Answer 42

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

Answer 43

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

Answer 44

where are the negatives of 6?

Answer 45

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

Answer 46

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

Answer 47

It's the second choice

Answer 48

yes!

Answer 49

i think you put the wrong format into your calc

Answer 50

Probably. But thank you

Answer 51

No problem