Using rules from Solve

*To*: mathgroup at smc.vnet.net*Subject*: [mg33680] Using rules from Solve*From*: post_12 at hotmail.com (postman)*Date*: Sat, 6 Apr 2002 00:48:57 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hey All: I appreciate any help with the following. I have a working solution, but don't understand why my first attempt failed. I'm using Solve to generate solutions to a set of simultaneous equations (the mass action equations in chemistry), then want to use the resulting solutions to calculate numerical values for specific values of the parameters. KdEqn={Kd==R*L/RL, RT=RL+R} Solve[KdEqn,RL,{RF}] gives me a rule, {{RL->L*RT/(Kd+L)}} and Replace[RL,Flatten[Solve[KdEqn,RL,{RF}]]] gives an expression L*RT/(Kd+L) that looks like what I would type on the right hand side of a function: Rl[L_] := L*RT/(Kd+L) The problem is that Rl[L_] := Replace[RL,Flatten[Solve[KdEqn,RP]{Rf}]] fails; Rl[1] does not substitute the value "1" for "L". However, Rl[L_] = Replace[RL,Flatten[Solve[KdEqn,RP]{Rf}]] works as I want. Why does the := construct fail here? Thanks for any help!