SOLUTION: If the fouth term of a geometric progression is -18 and the 5th term is 54, find a1 and R A) R= B) a1=

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Question 439206: If the fouth term of a geometric progression is -18 and the 5th term is 54, find a1 and R
A) R=
B) a1=
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
a%5B4%5D+=+-18
54+=+a%5B5%5D
==> r+=+a%5B5%5D%2Fa%5B4%5D+=+54%2F%28-18%29+=+-3.
==> a%5B4%5D+=+-18+=+a%5B1%5D%2A%28-3%29%5E3+=+-27a%5B1%5D
==. a%5B1%5D+=+%28-18%29%2F%28-27%29+=+2%2F3