Q. 53.7( 3 Votes )

# If , then S_{n} is equal to

A. 2^{n} – n - 1

B.

C.

D. 2^{n}– 1

Answer :

1 + 2 + 2^{2} + …….2^{r - 1}=1(2^{r} - 1)/2 - 1

1 + 2 + 2^{2} + …….2^{r - 1}=1(2^{r} - 1)

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