To evaluate any series of the formwe
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Expand the brackets and express as a sum of different summation terms. In this case we obtain
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Now use use the linearity properties of summation to obtain:
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Now use standard formulae to express each term in terms of n.
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Add the terms. Expand and simply the expression
Example Prove
1
2 There are no constants to take out.
3. Use the standard formulae.
.
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Subtract the second and third from the first. Expand and simplify.