Question

Please help MEEEE!!! What is the sum of the geometric sequence 8, –16, 32 … if there are 15 terms?

Answer 1

You have to find a general formula, or the nth term for the sequence

Answer 2

each time the number is multiplied by -2??

Answer 3

so multiply -2 x 12 from -32

Answer 4

Yes so the nth term would be (-1^n * -8n)

Answer 5

Plug in n=15, and you should get your answer.

Answer 6

-15 x -120? right?

Answer 7

1800?

Answer 8

Oh that was \[-1^{n}*(-8n)\]

Answer 9

hmmm

Answer 10

See if you plug in 1 into the above nth term, you would get 8, which is the first term
of the sequence

Answer 11

so the 15th term should be -120

Answer 12

im getting -120

Answer 13

oh haha cool, so thats it!!

Answer 14

oh wait, did you mean the sum

Answer 15

yea.....

Answer 16

Sum=8 + (-16) + 32 +...

Answer 17

oh nooo, im confused

Answer 18

oh sorry all you gotta do is add up the terms up to the 15th term.

Answer 19

i thought you just asked for the 15th term in the sequence

Answer 20

dayyum! Dddayyuum!!..... DDAAYYUMM!!! no prob thats easier then, thanks again for the help!!

Answer 21

No problems