Question
Find sum of first n terms: 2 + 6 + 12 + 20 + 30 +
…Solution
ATQ,
Series = n(n+1). Sum = Σn(n+1) = Σn² + Σn = [n(n+1)(2n+1)/6] + [n(n+1)/2] = n(n+1)(2n+1+3)/6 = n(n+1)(n+2)/3
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