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

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
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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