sum(r=1)^n r (n-r +1) is equal to :...

`sum_(r=1)^n r (n-r +1)` is equal to :

A

`(n(n^2 -1))/6`

B

`(n(n+1)(n+2))/6`

C

`(n(n^2-1))/2`

D

`(n(n+1)(n+2))/2`

Verified by Experts

The correct Answer is:

B

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