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Re: Don't understand behaviour of Solve[]


Hi,

say you have s system of equations

x+y==1
x-y==0

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}

Regards
  Jens

"Oliver Friedrich" <oliver.friedrich at tzm.de> 
schrieb im Newsbeitrag 
news:daitlm$sus$1 at smc.vnet.net...
> 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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