Q59 of 202 Page 9

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

Sn = 4n2 + 2n

First term, a = 4(1)2 + 2(1)


= 4 + 2 = 6


Sum of first two terms, S2 = 4(2)2 + 2(2)


a + a + d = 16 + 4


6 + 6 + d = 20


d = 8


Now the nth term, an = a + (n – 1) d


= 6 + (n – 1) 8


= 6 + 8n – 8


= 8n - 2


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