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MathGroup Archive 2003

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Re: differences in Solve with -1/2 and -0.5

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44431] Re: differences in Solve with -1/2 and -0.5
  • From: Bill Rowe <readnewscix at mail.earthlink.net>
  • Date: Sat, 8 Nov 2003 04:51:12 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

On 11/7/03 at 5:16 AM, Kenneth_Levasseur at uml.edu (Kenneth Levasseur) wrote:

> Can anyone give a good reason why there is a difference in the 
> following?  Preferably one that my students will understand.

> In[1]:=
> Solve[D[x E^(-x/2), x] == 0, x]
> Out[1]=
> {{x -> 2}}
> In[2]:=
> Solve[D[x E^(-0.5*x), x] == 0, x]
> General::dbyz:Division by zero.
> Out[2]=
> {}

Hmm... With Mathematica 5.0 running on MacOS 10.3 I get the same as you with exact arguements but I get {{x->2.}} for the second case. This certainly seems reasonable. What version of Mathematica are you using?
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