If the nth term of an A.P. is 2n + 1, then the sum of first n terms of the A.P. is

(a) n(n − 2)

(b) n(n + 2)

(c) n(n + 1)

(d) n(n − 1)

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Solution

Here, we are given an A.P. whose n^th term is given by the following expression, . We need to find the sum of first n terms.

So, here we can find the sum of the n terms of the given A.P., using the formula,

Where, a = the first term

l = the last term

So, for the given A.P,

The first term (a) will be calculated using in the given equation for n^th term of A.P.

Now, the last term (l) or the n^th term is given

So, on substituting the values in the formula for the sum of n terms of an A.P., we get,

Therefore, the sum of the n terms of the given A.P. is. So the correct option is (b).

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If the nth term of an A.P. is 2n + 1, then the sum of first n terms of the A.P. is (a) n(n − 2) (b) n(n + 2) (c) n(n + 1) (d) n(n − 1)

If the nth term of an A.P. is 2n + 1, then the sum of first n terms of the A.P. is

(a) n(n − 2)

(b) n(n + 2)

(c) n(n + 1)

(d) n(n − 1)