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 >