Question

3. What is the sum of a 6-term geometric sequence if the first term is 11, the last term is –11,264 and the common ratio is –4?

Answer 1

sum of n terms = a1 . r^n - 1
-------
r - 1

Answer 2

ok gimme a sec to try and figure it out.Is that a1 times r^n-1?

Answer 3

yes a1*(r^n - 1)

Answer 4

ok

Answer 5

Evert time I do it I get 9013.4

Answer 6

Every*

Answer 7

11*((-4)^6 - 1) / -5 ?

Answer 8

i make that -9009

Answer 9

Yeah but I put (-4^6-1)

Answer 10

Now my calculator says 9011.2

Answer 11

r = -4 so its (-4)^6

Answer 12

on most calculators you need to enter the brackets around the -4

Answer 13

That's what i did differently the second time and i got 9011.2

Answer 14

hmm - idk how you got that
the way i did it was
(-4)^6 = -1 = * 11 = / (-5) =

Answer 15

Ok im gunna try it again.

Answer 16

problem is - calculators vary

Answer 17

I finally got it! Thanks :)

Answer 18

good - ur welcome