given-the-sum-of-the-first-n-terms-of-an-A-P-is-n-2-the-sum-of-of-the-first-2n-terms-of-the-same-A-P-is-n-2-n-show-that-the-sum-of-the-first-4n-terms-is-4n-2-8n-4-

Question Number 34707 by mondodotto@gmail.com last updated on 10/May/18

given the sum of the first n terms

of an A . P is n^{2} the sum of

of the first 2 n terms of the

same A . P is n^{2} + n .

show that the sum of the first

4 n terms is 4 n^{2} - 8 n + 4 .

Commented by Rasheed.Sindhi last updated on 10/May/18

If sum of n terms of an AP = n^{2}

then

the sum of 2 n terms of the same AP = {(2 n)}^{2} = {4 n}^{2}

\neq n^{2} + n

The sum of 4 n terms = {(4 n)}^{2} = {16 n}^{2}

The sum of 4 n terms \neq 4 n^{2} - 8 n + 4

Commented by mondodotto@gmail.com last updated on 10/May/18

please recheck