SOLUTION: In a geometric sequence, the fourth term is -4, and the eighth term is -324. What is the tenth term?

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Question 695716: In a geometric sequence, the fourth term is -4, and the eighth term is -324. What is the tenth term?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
4th. term =-4

The nth term of a Geometric Progression is given by
Tn+=ar%5E%28n-1%29
t4=ar%5E3
-4=ar^3.................(1)
T8++=+ar%5E7
-324=ar^7...............(2)
Divide (2) by (1)
%28-324%2F-4%29+=+%28ar%5E7%2Far%5E3%29
81=+r%5E4
r=4


plug r=4 in (1)
-4=ar^3
-4=a*64
a=-1/16
t10= ar^9
t10+=+%28-1%2F16%294%5E9
t10 =-16384