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Re: ReplaceRepeated in case of non ordered expressions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg108099] Re: ReplaceRepeated in case of non ordered expressions
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Mon, 8 Mar 2010 06:14:33 -0500 (EST)

On 3/7/10 at 5:10 AM, arbiadr at gmail.com (Maria Davis) wrote:

>I have such equations:
>x=a+b
>y=c+d
>a=z+t
>b=y

In Mathematica, these are assignments, not equations. An
equation is written using "==" not "=" in Mathematica.

>I want to use mathematica in order to simplify x and  obtain:
>x=z+t+c +d I have used: [x,Listofequations] This function is
>available if I have equations written in the following order: x=a+b
>a=z+t b=y y=c+d

It is hard to comment on the above since you omitted the
function you tried. In any case, first create a list of equations

In[1]:= eqns = {x == a + b, y == c + d, a == z + t, b ==
= y};

then the desired result can be obtained using Eliminate as follows:

In[2]:= Eliminate[eqns, {a, b, y}]

Out[2]= c+d+t+z==x



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