Re: Simplification to Partial Fractions
- To: mathgroup at smc.vnet.net
- Subject: [mg59744] Re: Simplification to Partial Fractions
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Fri, 19 Aug 2005 04:32:28 -0400 (EDT)
- Organization: The University of Western Australia
- References: <de12oq$8l4$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <de12oq$8l4$1 at smc.vnet.net>,
"Jon Palmer" <jonathan.palmer at new.oxford.ac.uk> wrote:
> At first glance I can't make PolynomialReduce do what I need.
>
> Here is an example problem. Take the expression:
>
> u1 = A + (B*(x^2 - y^2)^2)/(x^2 + y^2) + (C*(y^2 - z^2)^2)/(y^2 + z^2)
> + (D*(-x^2 + z^2)^2)/(x^2 + z^2)
It's a bad idea to use capital letter constants, especially C and D (and
N), as these are used by Mathematica.
u1 = a + (b*(x^2 - y^2)^2)/(x^2 + y^2) +
(c*(y^2 - z^2)^2)/(y^2 + z^2) +
(d*(-x^2 + z^2)^2)/(x^2 + z^2)
> Now
>
> u2 = Factor[u1]
>
> How do you Simplify u2 back to the form of u1?
In this simple case, you can just use Collect:
Collect[u2, {a, b, c, d}]
but, of course, this will not work if these constants are numeric, or
unspecified.
Clearly, the problem is not fully specified. In this example, I can
eliminate the term involving a by multiplying it by any of the other
denominators and combining it with that term.
Cheers,
Paul
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