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प्रश्न
Find the sum to n terms of the series 12 + (12 + 22) + (12 + 22 + 32) + …
उत्तर
The given series is 12 + (12 + 22) + (12 + 22 + 32 ) + …
an = (12 + 22 + 32 +…….+ n2)
= nn+12n+16=n2n2+3n+16=2n3+3n2+n6=13n3+12n2+16n
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