SOLUTION: I've been trying this problem for a while now. Please help me find the sum of the geometric sequence where: a sub4=24 and a sub9= 768 and n=9. thank you

Algebra ->  Sequences-and-series -> SOLUTION: I've been trying this problem for a while now. Please help me find the sum of the geometric sequence where: a sub4=24 and a sub9= 768 and n=9. thank you      Log On


   

Question 420010: I've been trying this problem for a while now. Please help me find the sum of the geometric sequence where:
a sub4=24 and a sub9= 768 and n=9.
thank you
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

geometric sequence

a%5Bn%5D+=+a%5B1%5D%2Ar%5E%28n-1%29

a%5B4%5D+=+a%5B1%5D%2Ar%5E3+=+24 a%5B1%5D+=+24%2Fr%5E3

a%5B9%5D+=+a%5B1%5D%2Ar%5E8=+768

          24/r^3 *r^8 = 768

                  r^5 = 32

                  r = 2  and a%5B1%5D+=+3