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MathGroup Archive 2005

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Re: Assigning (really dumb question)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60993] Re: Assigning (really dumb question)
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 7 Oct 2005 03:37:39 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <di2ml8$8h0$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

Solve already return a list of replacement rules
and
r[q] /. qa

instead of

r[q] /. q->qa

should work.

Regards
  Jens

<vjp2.at at at.BioStrategist.dot.dot.com> schrieb im 
Newsbeitrag news:di2ml8$8h0$1 at smc.vnet.net...
| What the heck am I doing wrong? I've been away 
from Mathematica for a while.
|
| I can't get it to evaluate the expressions at 
the solved values.
|
| I feel so stupid.
|
| r[q_] := 1800 q - .006 q^2
| c[q_] := 12100000 + 800 q + .004 q ^2
|
| qa = Solve[ D[ r[q]-c[q] , q] == 0, q]
| r[q] /. q -> qa
| c[q] /. q -> qa
| r[q]-c[q] /. q -> qa
| D[r[q],q] /. q -> qa
| D[c[q],q] /. q -> qa
|
| qm = Solve[ c[q]/q - D[c[q] , q] == 0, q] [[2]]
| r[qm] /. q -> qm
| c[qm] /. q -> qm
| r[qm]-c[qm] /. q -> qm
| D[r[q],q] /. q -> qm
| D[c[q],q] /. q -> qm
|
|
| (PS, a while back I was asking how to fix DOS 
2.2.2 when it wasn't
| doing graphics and I was told it was no longer 
supported. Well, 2yrs
| later, dumbo me, realised I just had to cd into 
the math directory and
| all was fine.)
|
|
| - = -
|    Vasos-Peter John Panagiotopoulos II, 
Columbia'81+, Bio$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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