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 of the first

n

terms of a geometric progression with first term

a

and common ratio

r\,(r\neq1)

? (a)

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

(b)

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

(c)

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

(d)

\dfrac{n}{2}\bigl[2a+(n-1)r\bigr]