Re: simultaneous equations - eliminating variables and solving

*To*: mathgroup at smc.vnet.net*Subject*: [mg100216] Re: simultaneous equations - eliminating variables and solving*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Thu, 28 May 2009 06:49:17 -0400 (EDT)*References*: <gvlhv1$dq6$1@smc.vnet.net>

nninja wrote: > Hi, I am a postgrad student and completely new to mathematica, I am just starting to realise the possibilities. > > I am trying to do a chemical speciation calculation. > I have a set of simultaneous equations which represents the equilibria, mass balance, and charge balance in the system. > > I want to eliminate some of the variables, and then be able to solve for the remaining ones. > My system of equations looks like this: > a=b+c+d > e=f+g+c+2d > h=c/(bg) > i=d/(cg) > hi=d/(bg^2) > j=mg/f > k=lm > n+m+b+c=g+l > > This is what my formula looks like sofar. > > Solve[{a == b + c + d, e == f + g + c + 2 d, h == c/(b*g), > i == d/(c*g), h*i == d/(b*g^2), j == m*g/f, k == l*m, > n + m + b + c == g + l}, {g}] > > Basically, I can solve for the variable I want, but I am having trouble eliminating the ones I don't want (ie. I am getting an answer that is in terms of the wrong variables) > > I have been in the help files for ages, and don't really understand how to do this. > I would really appreciate some pointers!! > Thanks > Use the third argument to Solve. See http://reference.wolfram.com/mathematica/ref/Solve.html (But this particular set of equations doesn't seem to have a solution.)