ADNAN MUHAMMED

Grade 12,

1/2 [ 2{n(n+1)/2}^2 – n(n+1)(2n+1)/6 + n(n+1)/2 ] = 1/12 [ n(n+1) {3(n^2) + n +2}] Please show how??

1/2 [ 2{n(n+1)/2}^2 –  n(n+1)(2n+1)/6  + n(n+1)/2 ] = 
1/12 [ n(n+1) {3(n^2) + n +2}]
Please show how??
 

Grade:

2 Answers

Aditya Gupta
2081 Points
5 years ago
taking n(n+1)/6 common, we get
1/2 [ 2{n(n+1)/2}^2 –  n(n+1)(2n+1)/6  + n(n+1)/2]=[3n(n+1) – (2n+1)+3]*n(n+1)/12
=[3n^2+3n – 2n – 1+3]*n(n+1)/12
=1/12 [ n(n+1) {3(n^2) + n +2}]
Deepak Kumar Shringi
askIITians Faculty 4404 Points
5 years ago
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