Question
The sum of the series 12.2 + 22.3 + 32.4 + ........ to n terms is
Answer: Option B
:
B
Tπ = n2(n + 1) = n3 + n2
Sπ = ∑Tπ =∑n3 + ∑n2 = [n(n+1)2]2+ n(n+1)(2n+1)6
= n(n+1)2[n(n+1)2 + 2n+13] = n(n+1)(3n2+7n+2)12
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:
B
Tπ = n2(n + 1) = n3 + n2
Sπ = ∑Tπ =∑n3 + ∑n2 = [n(n+1)2]2+ n(n+1)(2n+1)6
= n(n+1)2[n(n+1)2 + 2n+13] = n(n+1)(3n2+7n+2)12
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