In an equation, the upper sum is Mi = 0+i(2/n)(adsbygoogle = window.adsbygoogle || []).push({});

and the lower sum is mi = 0+(i-1)(2/n)

So the question is why is it (i-1) for the lower sum and only i for the upper sum?

Any help is highly appreciated! ^_^

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# Homework Help: Upper and lower sums

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