Help on solving simultaneous non-linear equations using FindRoot.

*To*: mathgroup at smc.vnet.net*Subject*: [mg28514] Help on solving simultaneous non-linear equations using FindRoot.*From*: Youyan Li <youyanli at acsu.buffalo.edu>*Date*: Tue, 24 Apr 2001 01:48:50 -0400 (EDT)*Organization*: University at Buffalo*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I am trying to solve a 12-eqaution simultaneous non-linear equations using FindRoot function in Mathematica. This system of equations has 9 given parameter values and I need to solve for 12 unknown variables. But I have the problem in getting the system converged. If I take one endogenous variable out of the system and let it to be a given parameter, and also reduce the system into 9 equations, I can get a solution that looks like converged, but some of the variables have negative values, which are not what I expected. I expect all the variables have non-negative values. If I specify the range of the variables, usually I cannot get a solution at all. I wonder how to solve this problem. Or how to get an acceptable solution for this system? Is there any trick of solving large system of simultaneous non-linear equations using FindRoot? Thank you for the help in advance. Youyan Li