Find the rthterm of an A.P., the sum of whose first n terms is 3n2 +2n

It is given that the sum of n terms is 3n2 + 2n

To find: rth term of an AP, the sum of whose first term is 3n2 + 2n


So, the sum of n - 1 terms is 3(n - 1)2 + 2(n - 1)


formula TN = SN - SN - 1


So, Tr = 3r2 + 2r - [3(r - 1)2 + 2(r - 1)]


Tr = 3r2 + 2r - [3(r2 + 1 - 2r) + 2(r - 1)]


Tr = - 1 + 6r


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