1.

`sum_(k=1)^(oo) k(1-1/n)^(k-1) =`A. `n(n-1)`B. `n(n+1)`C. `n^(2)`D. `(n+1)^(2)`

Answer» Correct Answer - C
`underset(k=1)overset(oo)sumk(1-1/n)^(k=1)`
`=1-2(1-(1)/(n))^(1)+3(1+1/n)^(2)+"….."`
`= 1+2r+3t^(2)+"…"`
`= (1-t)^(-2)`
`= [1-(1-(1)/(n))]^(-2) = (1/n)^(-2) = n^(2)`


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