Question

If the sum of the first n terms of an ap is given by sn=(3n2-n) find its 20th term

Answer 1

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.

Answer 2

Answer:

146 IS THE ANSWER

Explanation:

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