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 If r=1nTr=3n1, then find the sum of m=1n1Tm

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a
3413n
b
341−13n
c
341−12n
d
341−15n

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detailed solution

Correct option is B

∑r=1nTr=3n−1⇒Tr=3r-1-3r−1−1=3r−1(3−1)=23r−1⇒1Tr=12×13r−1⇒∑r=1n 1Tr=12∑r=1n 13r−1=121−13n1−13=341−13n


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