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Re: What's wrong with this assuming?

• To: mathgroup at smc.vnet.net
• Subject: [mg111138] Re: What's wrong with this assuming?
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Wed, 21 Jul 2010 07:15:12 -0400 (EDT)

Try:

  Assuming[x^2 + x == h, Simplify[(x^2 + x)^2 + h]]

Your original expression means the same thing as:

   FullSimplify[ Assuming[x^2 + x == h, (x^2 + x)^2+h] ]

And that's clearly not what you intend, which is:

   Assuming[[x^2 + x == h, FullSimplify[(x^2 + x)^2 + h] ]

Actually, Simplify will do nicely instead of FullSimplify here.

On 7/20/2010 3:43 AM, Sam Takoy wrote:
> Hi,
>
>
> I have a situation where I have to simplify an expression that contains
> x and h, but x is given implicitly by h, so I can't explicitly eliminate
> it. So here's a simpler example that I'm trying and it does nothing:
>
> Assuming[x^2 + x == h, (x^2 + x)^2+h] // FullSimplify
>
> Is there a way to make this work?
>
> Thanks!
>

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
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