Posted by **Wayne** on Thursday, November 11, 2010 at 9:22pm.

Use the method of differences to prove the following formulas

1) ∑_(r=1)^n▒〖r=(n(n+1))/2〗

2) ∑_(r=1)^n▒〖r^2=(n(n+1)(2n+1))/6〗

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