# If the sum of n terms of an A.P.

Question:

If the sum of n terms of an A.P. be 3 n2 − n and its common difference is 6, then its first term is

(a) 2

(b) 3

(c) 1

(d) 4

Solution:

(a) 2

$S_{n}=3 n^{2}-n$

$\Rightarrow S_{1}=3(1)^{2}-1$

$\Rightarrow S_{1}=2$

$\therefore a_{1}=2$