Sum formulaHardQuestion 210044
Question
The sum of n terms of the series whose nth term is n² + n + 1 is:
- An(n+1)(n+2)/3 + n
- Bn(n²+2n+3)/3
- Cn(n+1)(2n+1)/6 + n(n+1)/2 + n
- DAll of these are equivalentCorrect
Correct answer
All of these are equivalent
Explanation
Sₙ = Σ(n²+n+1) = n(n+1)(2n+1)/6 + n(n+1)/2 + n = n[n(2n+1)/6 + (n+1)/2 + 1]. These simplify to the same expression.