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Homework Statement
a) nƩr2(r-1)r=1
Homework Equations
Using the summation series formulae...
The Attempt at a Solution
So far I have got:
r2(r-1) = r3-r2
Ʃr3 = [itex]\frac{1}{4}[/itex]n2 (n+1)2
Ʃr2 = [itex]\frac{1}{6}[/itex]n(n+1)(2n+1)
Therefore,
Ʃr3-r2 = [itex]\frac{1}{4}[/itex]n2 (n+1)2 - [itex]\frac{1}{6}[/itex]n(n+1)(2n+1)
But how do I subtract these two massive things from each other??
Thanks.