Constraint definition is not valid: WHY?

*To*: mathgroup at smc.vnet.net*Subject*: [mg131358] Constraint definition is not valid: WHY?*From*: aless.bolli at gmail.com*Date*: Mon, 1 Jul 2013 05:48:38 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net

I am tring to use Nmaximize in Mathematica This is How I proceeded: 1) define a list of parameters: Par = {a->1, b->3, etc}; 2) define two functions: f1: v1=express./Par f2: v2=express./Par After this the expression are numerical except for the variables: V1=f(e1,x) and V2=f(e2,x) The objective function to be maximized is V1/(e1+e2) I defined the constraint as constr=V1-V2; then I used the Nmaximize: NMaximize[{objopt > 0, constr == 0}, {e1, e2, x}, Method -> NelderMead] I obtained the following error: NMaximize::bcons: "The following constraints are not valid: "expression". Constraints should be equalities, inequalities, or domain specifications involving the variables" I checked that only those variables are present in the constraint and objective function (other are numerical parameters) I do not understand why this error appears can someone help me? Thank you Alex

**Follow-Ups**:**Re: Constraint definition is not valid: WHY?***From:*Bob Hanlon <hanlonr357@gmail.com>