The seconds term of a geometric series is 4 while the fou...
The seconds term of a geometric series is 4 while the fourth term is 16. Find the sum of the first five terms
60
62
54
64
Correct answer is B
T2 = 4, T4 = 16
Tx = arn-1
T2 = ar2-1 = 4 i.e. ar3 = 16, i.e. ar = 4
T4 = ar4-1
therefore, T4Tr = ar3ar = 164
r2 = 4 and r = 2
but ar = 4
a = 4r = 42
a = 2
Sn = a(rn−1)r−1
S5 = 2(25−1)2−1
= 2(32−1)2−1
= 2(31)
= 62
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