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Question
Find the sum to infinity of 9 + 3 + 1 + ….
Solution
9 + 3 + 1 + ….
a = 9, r = `3/9 = 1/3 < 1`
S∞ = `"a"/(1 - "r")`
= `9/(1 - 1/3)`
= `(9/(3 - 1))/3`
= `(9/2)/3`
= `9 xx 3/2`
= `27/2`
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