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MathGroup Archive 1999

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Re: Simplifying constants...bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18559] Re: [mg18489] Simplifying constants...bug?
  • From: calvitti at boes.ces.cwru.edu
  • Date: Sat, 10 Jul 1999 02:18:50 -0400
  • Organization: Case Western Reserve University
  • References: <7m3l22$shp@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

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?

+------------------------------------------+
  alan c                            
  systems and control engineering
  case western reserve university   
  
  calvitti at alpha.ces.cwru.edu    
+------------------------------------------+



"Ersek, Ted R" <ErsekTR at navair.navy.mil> writes:

> Morten G. Dyndgaard wrote:
> -----------------------------
> I am working with some annoyingly long equations that I want to simplify
> by including one set of parameters in a constant (or function) A, and
> another in B and so on.
> 
> You can easily do:
> A = b+c+d+e
> 
> but what I want to do is the reverse:
> b+c+d+e = A
> -----------------------------
> 
> This should help.
> In[1]:=
> expr=a+b+b1+c+c1+d+d1+e;
> 
> 
> In[2]:=
> expr/.a+b+c+d+e->A
> 
> Out[2]=
> A+b1+c1+d1
> 
> 
> Regards,
> Ted Ersek


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