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MathGroup Archive 2007

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Re: Combining Fractions with Identical Denominator?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81023] Re: [mg80994] Combining Fractions with Identical Denominator?
  • From: Sseziwa Mukasa <mukasa at jeol.com>
  • Date: Sat, 8 Sep 2007 03:51:38 -0400 (EDT)
  • References: <200709070607.CAA06723@smc.vnet.net>

On Sep 7, 2007, at 2:07 AM, Jung-Tsung Shen wrote:

> I have a sum of a series of fractions (symbolic) of about 50 terms.
> How can I have Mathematica to sum up those with the same denominator?
> By inspection, there are about 5 different denominators. I have wrote
> a simple rule to compare the denominator term by term, but it's rather
> slow. Moreover, sometimes the denominators differ only with a +/-
> sign, a numerical factor (say, 1/2), or a complex i.
>
> In mathematical terms, I have a series in the following form (the
> number of terms can vary):
>
> N1/D1 + N2/D2 + ... + N50/D50
>
> These Di's form 5 different groups. Within each group, there are
> proportional to each other. How could I sum up this series such that
> those terms with Di in the same group is summed?

Sort the terms according to the denominator group then split the  
lists and apply together to each sublist.

Regards,

Ssezi


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