Question

the sum of the first n terms of an ap is given by sn=3n2-n.find it's nth term
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Answer 1

Step-by-step explanation:

Given, sum of first n terms of an AP, Sn = 3n2 – n

Sn = 3n2 – n

Replacing n by n – 1, we get

Let the nth term of AP be an.

Now,put n = 1 in an, we get a = 6×1−4 = 2put n = 2 in an, we get a2 = 6×2−4 = 8put n = 3 in an, we get a3 = 6×3−4 = 14and so on.So, required AP is, 2,8,14,.....

Putting n = 25, we get

a25 = 6 × 25 – 4 = 150 – 4 = 146

Thus, the 25th term of the given A.P. is 146.