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

• To: mathgroup at smc.vnet.net
• Subject: [mg44399] Re: differences in Solve with -1/2 and -0.5
• From: "David W. Cantrell" <DWCantrell at sigmaxi.org>
• Date: Sat, 8 Nov 2003 04:50:44 -0500 (EST)
• References: <boftfo\$5ph\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```"Kenneth Levasseur" <Kenneth_Levasseur at uml.edu> 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]=
> {}

Using the current version of Mathematica, I get

Out[2]= {{x -> 2.}}

just as one would expect.

David

```

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