Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Don't understand behaviour of Solve[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58567] Re: Don't understand behaviour of Solve[]
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 8 Jul 2005 00:45:58 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <daitlm$sus$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

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
> 



  • Prev by Date: Re: Using InterpolatingFunction from NDSolve
  • Next by Date: Re: Mathematica query
  • Previous by thread: Re: Don't understand behaviour of Solve[]
  • Next by thread: Re: Don't understand behaviour of Solve[]