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MathGroup Archive 2001

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Re: rewriting a fraction a/b==c/d + e/f

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31007] Re: rewriting a fraction a/b==c/d + e/f
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Tue, 2 Oct 2001 01:20:42 -0400 (EDT)
  • References: <9p93dn$oce$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Okke,

    Apart[1/((x-1)(x^2+x+1))]

        1/(3*(-1 + x)) + (-2 - x)/(3*(1 + x + x^2))

In this case, the Help Browser helps:
- select Partial Fractions
- menu>Help>Find Selected Function.

Also

SolveAlways[1/((x-1)(x^2+x+1))== A/(x-1) + (B x+C)/(x^2+x+1),x]

{{A -> 1/3, B -> -(1/3), C -> -(2/3)}}

A/(x-1) + (B x+C)/(x^2+x+1)/.%[[1]]

1/(3*(-1 + x)) + (-(2/3) - x/3)/(1 + x + x^2)

--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

"Okke" <kroosu at tref.nl> wrote in message news:9p93dn$oce$1 at smc.vnet.net...
> hello,
> i'm trying the mathematica demo by doing some basic mathematics.
> now i'm stuck at rewritting a fraction.
> could somebody please help me by telling  me how to rewrite:
>
> 1/((x-1)(x^2+x+1)) to A/(x-1) + (Bx+C)/(x^2+x+1)
> or do i have to do that manualy?
> and can mathematica find  the values for A, B and C ?
> Solve[eqn1==eq2,{A}] doesnt solve the problem, and subsituting
> x with 1 doesnt either.
>
> tia,
> --
> Okke <kroosu at tref.nl>
>




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