Question 68547
xyz^0 - 7x^2y^2 + 2x^3x^-2yz^-2 + 5xy^-1y^0
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z        xyz       z^-1x^0        zy^-2
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I would first of all try to simplify the problem, as follows:
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[xy/z] - [7xy/z] + [2xy/z] + [5xy/z]
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Now you see the common denominator is "z" and each fraction has the 
same denominator so we can add the numerators and write the sum over z
as follows:
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= [xy-7xy+2xy+5xy]/z

=[xy]/z
Cheers,
stan H.