Re: What's going on here??

• To: mathgroup at smc.vnet.net
• Subject: [mg33520] Re: [mg33502] What's going on here??
• From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
• Date: Mon, 25 Mar 2002 03:44:54 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```This is certainly a bug. In your example c does not occur in the formula
that is being simplified so the problem looks innocuous but a small
modification makes it look more serious:

In[1]:=
Simplify[5(a+a b-a(1+b))*c==0,{c>5}]

Out[1]=
False

Without the assumption there is no problem. Also,  the following give
the correct result:

In[2]:=
Simplify[5(a+a b-a(1+b))*c>=0,{c>5}]

Out[2]=
True

In[3]:=
Simplify[5(a+a b-a(1+b))*c<=0,{c>5}]

Out[3]=
True

Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/

On Sunday, March 24, 2002, at 06:43  AM, Mat Bowen wrote:

> Hello,
>
> I was getting weird results today and reduced the code producing them to
> this:
>
> Clear[a,b,c]
> Simplify[5(a+a b-a(1+b))==0,{c>5}]
>
> False
>
>
> Surely thatÏ?s not right?! Can anyone explain whats going on?
>
> Thanks, and apologies if this is already known.
>
> Mat Bowen
> Department of Mathematics
> Loughborough University
>
>
>
>

```

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