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

• To: mathgroup at smc.vnet.net
• Subject: [mg44396] Re: differences in Solve with -1/2 and -0.5
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Sat, 8 Nov 2003 04:50:41 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <boftfo\$5ph\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

the algorithm used by Solve[] divide by zero because it
does not see the common exponential factor. Help it with

Solve[Simplify[D[x E^(-0.5*x), x]] == 0, x]

Regards
Jens

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]=
> {}
>
> Ken Levasseur
> Math. Sciences
> UMass Lowell

```

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