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