Question

Find the sum to n terms of the series 1^2+4^2+7^2+..........

Answer 1

1^2=1

4^2=8

7^2=49

Thus ap : 1,8,49....

But as we can see that Common difference is not the Same, these terms do not form an A.P

8-1=7 { a2-a1}

49-8=41 {a3-a2}

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