Re: Assigning (really dumb question)

• To: mathgroup at smc.vnet.net
• Subject: [mg60994] Re: [mg60988] Assigning (really dumb question)
• From: Andrzej Kozlowski <andrzej at yhc.att.ne.jp>
• Date: Fri, 7 Oct 2005 03:37:39 -0400 (EDT)
• References: <200510060808.EAA08545@smc.vnet.net>
• Reply-to: Andrzej Kozlowski <andrzej at akikoz.net>
• Sender: owner-wri-mathgroup at wolfram.com

```The output of Solve, (qa) ia already a list of rules so q->qa is not
what you want. Just use r[q]/.qa etc.

Andrzej Kozlowski

On 6 Oct 2005, at 17:08, vjp2.at at at.BioStrategist.dot.dot.com wrote:

> What the heck am I doing wrong? I've been away from Mathematica for
> a while.
>
> I can't get it to evaluate the expressions at the solved values.
>
> I feel so stupid.
>
> r[q_] := 1800 q - .006 q^2
> c[q_] := 12100000 + 800 q + .004 q ^2
>
> qa = Solve[ D[ r[q]-c[q] , q] == 0, q]
> r[q] /. q -> qa
> c[q] /. q -> qa
> r[q]-c[q] /. q -> qa
> D[r[q],q] /. q -> qa
> D[c[q],q] /. q -> qa
>
> qm = Solve[ c[q]/q - D[c[q] , q] == 0, q] [[2]]
> r[qm] /. q -> qm
> c[qm] /. q -> qm
> r[qm]-c[qm] /. q -> qm
> D[r[q],q] /. q -> qm
> D[c[q],q] /. q -> qm
>
>
> (PS, a while back I was asking how to fix DOS 2.2.2 when it wasn't
> doing graphics and I was told it was no longer supported. Well, 2yrs
> later, dumbo me, realised I just had to cd into the math directory and
> all was fine.)
>
>
>                 - = -
>     Vasos-Peter John Panagiotopoulos II, Columbia'81+, Bio\$trategist
>           BachMozart ReaganQuayle EvrytanoKastorian
>        http://ourworld.compuserve.com/homepages/vjp2/vasos.htm
>   ---{Nothing herein constitutes advice.  Everything fully
> disclaimed.}---
>    [Homeland Security means private firearms not lazy obstructive
> guards]
>  [Fooey on GIU,{MS,X}Windows 4 Bimbos] [Cigar smoke belongs in veg
> food group]
>
>

```

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