Question

Math Analysis:
Find the sum of the given geometric series
12-6+3-3/2+...

Answer 1

\( \color{Black}{\Rightarrow \Large a{ 1 - r^n \over 1 - r} }\)

The ratio is -1/2 as we multiply by -1/2 all the time to get the next term in the sequence.
a would be the first terms i.e 12.
n would be the number of terms.

Answer 2

Is this an infinite sequence?

Answer 3

idk.. i haven't really learned this in class, our teacher just gave it to us for our final which is gunna start in 2 hrs..

Answer 4

it says the answer is 8 but idk how they got that answer

Answer 5

Honestly I have no idea too

Answer 6

Apply the formula:
S = a_1 / ( 1 -r)
= 12 / 1.5 = 8

Answer 7

why do we divide 12 by 1.5?

Answer 8

where did the 1.5 come from

Answer 9

Can you use this formula and @ParthKohli's instruction:

Answer 10

can u explain it to me.. cause he said he had no clue what he was doing

Answer 11

There is supposed to be a 1 - r^n....I don't know what n is supposed to be :/

Answer 12

We know, it just because you confused us, and keep closing your post !?!

Answer 13

so what would be n

Answer 14

what was r in the first place

Answer 15

S = a_1 / ( 1 -r)
a_1 = 12
r = -1/2

Answer 16

that made u get 1.5
from "a/1-r"

Answer 17

whats the _ between 1 and a mean?

Answer 18

im still confused

Answer 19

Work out here, plug in the number, so I know what make you confused!

Answer 20

ok so the formula is
S=a1/1-r?

Answer 21

a1=12
and to get r i would use that formula up there? "S=a1/1-r"

Answer 22

I mean ratio

Answer 23

which is 6?

Answer 24

r=1.5? but how

Answer 25

.5

Answer 26

so r=.5

Answer 27

sorry i mean -.5

Answer 28

then why do we divide by 1.5?

Answer 29

if r=-.5

Answer 30

1 - ( -.5 ) = ....?

Answer 31

k, i got it

Answer 32

All you need is the formula!

Answer 33

the formula for r=a2/a1?

Answer 34

Your post is so confusing, make sure post the answer, so we can manage to help you out.
Pls don't keep closing your post, jumping all around !!!

Answer 35

wait so the formula for r=a2/a1

Answer 36

You don't read at all, do you ???
S = a_1 / ( 1 -r)
a_1 = 12
r = -1/2

Answer 37

-1 would be -6
2 would be 12

Answer 38

im sorry, i'm really tired rite now.. didn't get any sleep :\

Answer 39

im sorry it's just hard atm when you don't sleep

Answer 40

Because we already try so much to help you out, however you are the one neglect it !!!

Answer 41

i just thought r=a2/a1 because we divided -6/12 to get our answer which was .5

Answer 42

element 2/element 1

Answer 43

r = any ratio between the next 2 numbers!

Answer 44

what ifi replaced -6 with 24?

Answer 45

-24? would i divide -24/12?

Answer 46

or would it still be the same .5

Answer 47

-.5

Answer 48

12-6+3-3/2+..
But in this series the first one is 12, you can't break its rule!

Answer 49

i know what i'm trying to say is what if the equation was like this
12-24+3-3/2+...
would r still equal -.5?

Answer 50

Yes, all the ratio should be equal, that's from geometric series definition!

Answer 51

so it doesn't have to do with the 2ndnumber being multiplied by the 1st but the ratio between the two numbers

Answer 52

*being divided*

Answer 53

It's just all the basic from the formula!
I'll leave it for you to learn for your own long run benefits!

Answer 54

what if those two number were like in decimals..?

Answer 55

like 12.5 and 7.5 how would i get the ratio from there?