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Re: Don't understand behaviour of Solve[]

  • To: mathgroup at
  • Subject: [mg58567] Re: Don't understand behaviour of Solve[]
  • From: "Jens-Peer Kuska" <kuska at>
  • Date: Fri, 8 Jul 2005 00:45:58 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <daitlm$sus$>
  • Sender: owner-wri-mathgroup at


say you have s system of equations


if you solve it for y only you get y->1-x and y->x
this is an contradiction because for a general x 
this is not true,
while if you solve it for
{x,y} you get the solution {x->1/2,y->1/2}


"Oliver Friedrich" <oliver.friedrich at> 
schrieb im Newsbeitrag 
news:daitlm$sus$1 at
> Hallo,
> I have a problem understanding the general 
> behaviour of the Solve[]
> function.
> I have a set of equations with the variables 
> a,b,c,d and k.
> Evaluating Solve[set,k] or Solve[set,{a,b}] 
> returns with {}, whereas Solve
> [set,{k,b,c,d}] returns solutions for k,b,c and 
> d.
> My question: Why does Solve returns no solution 
> when searching only for k
> for example and why is there a solution for 
> several variables? I thought
> that giving a list of variables just means that 
> I want to search for all of
> them. But the procedure doesn't seem to be 
> independant from one variable to
> another.
> What kind of information contains my list of 
> variables except my wish to
> solve for these?
> Many thanks
> Oliver friedrich

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