find the common ratio in a geometric sequence if the first term is one-third and the 8th term is 128/3

The n'th term of a geometric sequence is given by a*r^n-1, where a is the first term and r is the common ratio.

 

(1/3)r^8-1 = 128/3

 

r⁷ = 128

 

So r = 2

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