Q1 of 102 Page 429

If the sum of n terms of an AP is given by Sn = (2n2 + 3n), then find its common difference.

Given: Sn = (2n2 + 3n)

To find: find common difference


Put n = 1 we get


S1 = 5 OR we can write


a = 5 …equation 1


Similarly put n = 2 we get


S2 = 14 OR we can write


2a + d = 14


Using equation 1 we get


d = 4


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