Question

choose the correct answer.

(2² – 2) + (3² – 3) + (4² – 4) + ...... + (n² – n)=

a)n(1-n)(1-2n)/6 b)n(n+1)(n-1)/6
c)n(n-1)(n+2)/6 d)None of these
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Answer 1

i think c is a rigth answer