Re: Using rules from Solve

• To: mathgroup at smc.vnet.net
• Subject: [mg33697] Re: Using rules from Solve
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 9 Apr 2002 01:01:59 -0400 (EDT)
• Organization: Universitaet Leipzig
• References: <a8m2vj\$oag\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

can you make postings without obvious syntax errors ?
and do you mean ReplaceAll[] instead of Replace[] ?

Regards
Jens

postman wrote:
>
> 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!

```

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