Which of the following is the correct expression for the sum of the first terms of an…

MATHEMATICS · Single correct · CBSE · Mathematics · Arithmetic Progressions · Arithmetic Progressions

Problem

Which of the following is the correct expression for the sum

S_n

of the first

n

terms of an arithmetic progression with first term

a

and common difference

d

? (a)

S_n = \dfrac{n}{2}[a + (n-1)d]

(b)

S_n = \dfrac{n}{2}[2a + nd]

(c)

S_n = n[2a + (n-1)d]

(d)

S_n = \dfrac{n}{2}[2a + (n-1)d]