Question

The sum of the first 26 terms of an AP 1, 3, 5, 7, ... is -​

Answer 1

Given:

First term, a = 1

Common difference, d = a2 - a1 = 3 - 1 = 2

Number of terms, n = 26

Formula:

an = a + ( n - 1 )d

Sn = n/2 ( a + an )

To Find:

The sum of the first 26 terms.

Explanation:

We need to find what's the last term of the AP.

a26 = 1 + ( 26 - 1 )(2)

a26 = 1 + 25(2)

a26 = 1 + 50 = 51

The last term of the AP is 51.

Now, we need to find the sum of the first 26 terms.

S26 = 26/2 ( 1 + 51 )

S26 = 13 ( 52 )

S26 = 676

Answer:

The sum of the first 26 terms of the AP is 676 .

Answer 2

Answer:

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Step-by-step explanation:

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