SOLUTION: Find S9 of a geometric series if t1 = 2 and t6 = 486.

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Question 1202472: Find S9 of a geometric series if t1 = 2 and t6 = 486.
Answer by mananth(16946) About Me  (Show Source):
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Find S9 of a geometric series if t1 = 2 and t6 = 486.


tn = ar^(n-1)
n= number of terms
a = first term
t1=2
t6 = 2*r^5= 486
r^5 =243
r=3
Sum of n terms =Sn+=+a%2A%281+-+r%5En%29+%2F+%281+-+r%29
S9 = 2*(1-3^9)/(1-3)
= 19682