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

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

Problem

Which of the following gives the sum

S_n

of the first

n

terms of a geometric progression whose first term is

a

and common ratio

r

(r\ne1)

? (a)

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

(b)

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

(c)

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

(d)

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