Re: Transformation rule problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg58158] Re: Transformation rule problem*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Mon, 20 Jun 2005 05:21:36 -0400 (EDT)*Organization*: The University of Western Australia*References*: <d8rnfg$l4b$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <d8rnfg$l4b$1 at smc.vnet.net>, Oliver Buerschaper <groo137vy at yahoo.co.uk> wrote: > I'm stuck with a problem concerning transformation rules and was > wondering whether somebody could give me a hint on this. I wouldn't > mind a complete solution either ;-) Here's the problem: > > In a sum like for example > > a^2 b^4 + a^3 b + a^5 + a^5 b > > I'd like to replace every instance of the product (a b) by a different > expression, let's call it d. Thus my result should look like > > d^2 b^2 + a^2 d + a^5 + a^4 d > > This replacement is required to work for arbitrary a and b (especially > when they're functions). I've already tried some simple transformation > rules but they couldn't do the job. Others have shown how to do this using replacement rules. For this type of problem though, I think that PolynomialReduce is the right tool: PolynomialReduce[a^2 b^4 + a^3 b + a^5 + a^5 b, a b - d, {a, b}] // Last Cheers, Paul -- Paul Abbott Phone: +61 8 6488 2734 School of Physics, M013 Fax: +61 8 6488 1014 The University of Western Australia (CRICOS Provider No 00126G) AUSTRALIA http://physics.uwa.edu.au/~paul http://InternationalMathematicaSymposium.org/IMS2005/