Q8 of 178 Page 559

The sum of first n terms of an AP is (4n2 + 2n). The nth term of this AP is

Let Sn denotes the sum of first n terms of an AP.


Sum of first n terms = Sn = 4n2 + 2n


Then nth term is given by: an = Sn - Sn - 1


∴ an = (4n2 + 2n) - [4(n - 1)2 + 2(n - 1)]


= (4n2 + 2n) - [4(n2 + 1 - 2n) + 2n - 2]


= 4n2 + 2n - 4n2 - 4 + 8n - 2n + 2


= 8n - 2

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