Question

The sum of the first n terms of an AP is given by Sn= (3n²-n). Find its
(CBSE 2005C
(i) nth term, (ii) first term and (iii) common difference.
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Answer 1

Step-by-step explanation:

OKAY

So S¹=. (3×1²-1)

= 3-1 =2

a =2

S2=(3×2²-2)

= (3×4-2)

= 12-2. =10

we know S2 = a + a + d [ first term + second term]

10= 4+d

10-4=d

6=d

an= a+(n-1)d

= 2+(n-1)6

=2+6n-6

=6n-4