Which of the following correctly gives the sum of the first terms of a geometric…

MATHEMATICS · Single correct · CBSE · Mathematics · Sequences and Series · Sequences and Series

Problem

Which of the following correctly gives the sum

S_n

of the first

n

terms of a geometric progression whose first term is

a

and common ratio

r\;(r\neq1)

? (a)

a\dfrac{r^{n}-1}{1-r}

(b)

ar^{\,n-1}(r-1)

(c)

a\dfrac{r^{n}-1}{r-1}

(d)

a\dfrac{r^{n-1}-1}{r-1}