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Find the sum to n terms of the series: 1...

Find the sum to `n` terms of the series: `1+5+12+22+35+`

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Verified by Experts

Given,`1+5+12+22+35+`
Differences are 4,7,10,13,...
So it is in AP.
Let `T_n=an^2+bn+c`
so,`T_1=a+b+c=1`
`T_2=4a+2b+c=5`
`T_3=9a+3b+c=12`
...
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