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If alpha is the nth root of unity then p...

If `alpha` is the nth root of unity then prove that `1+2 alpha+ 3 alpha^2+….` upto n terms `=(-n)/(1-alpha)`

A

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

B

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

C

`(n)/(1-alpha)`

D

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

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