(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

a)^{n}Ʃr^{2}(r-1)_{r=1}

2. Relevant equations

Using the summation series formulae...

3. The attempt at a solution

So far I have got:

r^{2}(r-1) = r^{3}-r^{2}

Ʃr^{3}= [itex]\frac{1}{4}[/itex]n^{2}(n+1)^{2}

Ʃr^{2}= [itex]\frac{1}{6}[/itex]n(n+1)(2n+1)

Therefore,

Ʃr^{3}-r^{2}= [itex]\frac{1}{4}[/itex]n^{2}(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.

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# Homework Help: Summing Series (Sigma Notation)

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