If is the first term

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

Problem

a_1

is the first term,

a_n

the

n

-th term and

S_n

the sum of the first

n

terms of an arithmetic progression, which statement is always true? (a)

S_n = n\,(a_1 + a_n)

(b)

S_{n+1} = S_n + a_n

(c)

S_n=\dfrac{n}{2}(a_1+a_n)

(d)

S_n=\dfrac{n}{2}(a_n-a_1)