1. What is the sum of the geometric sequence 8, –16, 32 … if there are 15 terms?

Question

1.	What is the sum of the geometric sequence 8, –16, 32 … if there are 15 terms?

anonymous · Answer

how do i do this?

anonymous · Answer

anyone?

anonymous · Answer

use the formula

Sum   = a r^n  -    1
                --------
                      r - 2

where a = first term, n = number of terms and r = common ratio

common ration  =  -16 / 8  = -2

anonymous · Answer

how did u know the common ratio

anonymous · Answer

8-2^15-1
---------
-2-2           ?

anonymous · Answer

(8 * -2^15) - 1
      ---------
         -2-2

anonymous · Answer

terms in a GP are of the form a,ar,ar^2,ar^3

so r = common ratio =  ar /a 
in the above  a = 8 and ar = -16

anonymous · Answer

sum =[ 8* -32768  - 1] /  -4

anonymous · Answer

65536.25
\
- sum of GP with a common  ratio  integer >|1|   gets bigger pretty quickly

anonymous · Answer

need any more help?