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If alpha (!=1) is a nth root of unity th...

If `alpha (!=1)` is a nth root of unity then `S = 1 + 3alpha+ 5alpha^2 + .......... `upto n terms is equal to

A

`(2n)/(1-alpha)`

B

`-(2n)/(1-alpha)`

C

`(n)/(1-alpha)`

D

`-(n)/(1-alpha)`

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