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Question 40. The sum of the first n terms of an A.P. is 4n2 + 2n. find the nth term of this A.P.

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This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6

In this question we have been given that The sum of the first n terms of an A.P. is 4n2 + 2n.

Now we have to find the nth term of this A.P

CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 40

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1 Answer

  1. Given Sn = 4n2 + 2n,

    On putting n = 1, we get the first term(a), S1 = a = 4(1)+ 2(1) = 6

    On putting n = 2 gives S2 = a + a + d = 4(2)+ 2(2) = 20

    => d = 20 – 2a

    => d = 20–12 = 8

    By using the formula of nth term of an A.P.

    an = a + (n – 1)d

    So,

    = 6 + (n – 1)8

    = 6 + 8n – 8

    = 8n – 2

    Hence, the nth term of the given A.P. is 8n – 2.

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