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MathGroup Archive 1999

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Re: Re: Simplifying constants...bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18596] Re: [mg18559] Re: [mg18489] Simplifying constants...bug?
  • From: BobHanlon at aol.com
  • Date: Tue, 13 Jul 1999 01:01:28 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Alan,

This is done using version 4; however, I believe the results will be the same 
in version 3.

(a + c*d)/(c*d) //. c*d -> -z

(a - z)/(c*d)

FullForm[%]

Times[Power[c, -1], Power[d, -1], Plus[a, Times[-1, z]]]

Note that the FullForm does not include the product c*d.  Ingeneral, I find 
that it works better to structure a replacement such that a single variable 
rather than an expression is being replaced.

(a + c*d)/(b + c*d) //. c -> -z  /d

(a - z)/(b - z)

(a + c*d)/(c*d) //. c -> -z/d

-((a - z)/z)

Bob Hanlon

In a message dated 7/10/99 8:40:24 AM, calvitti at boes.ces.cwru.edu writes:

>here's some intersting behavior in 3.0:
>
>    (a + c*d)/(b + c*d) //. c*d -> -z   
>
>gives (as expected):
>
>    (a - z)/(b - z)
>
>yet
>
>    (a + c*d)/(c*d) //. c*d -> -z
>
>no longer simplifes the denominator:
>
>    (a+b-z)/(c*d)
>
>anyone know why?
>


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