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Question
Find the sum of first n terms of the G.P.
256, 64, 16, …
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Solution
256, 64, 16, …
a = 256
r = `64/256 = 4/16 = 1/4 < 1`
Sn = `("a"(1 - "r"^"n"))/(1 - "r")`
= `256[(1 - (1/4)^"n")/(1 - 1/4)]`
= `256([1 - (1/4)^"n"])/(3/4)`
= `1024/3[1 - (1/4)^"n"]`
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