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MathGroup Archive 2006

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Re: Simplifying in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71121] Re: Simplifying in Mathematica
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Thu, 9 Nov 2006 03:37:18 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <eish5b$nq1$1@smc.vnet.net>

330006 at gmail.com wrote:
> I have a function which is a sum of many terms which look like this:
> 
> (2*(B-b)^2 - 2*(A-a)*c*d^2)/(4*b^2*(1-c*2)*d^2)
> 
> I think the function is actually equal to 0, but I have a hard time in
> trying to simplify it in Mathematica. Any ideas or commands I should
> try? Any suggestions in general about simplifying formulas will also
> be greatly appreciated!
> 
> Thanks a lot!
> 
Not knowing the real expression, I can only guess. If the function is a 
sum of rational expression, it will be equal to zero if its numerator is 
itself equal to zero. So you could start by extracting the numerator of 
the function and from there try to simplify it further (Simplify, 
Expand, PowerExpand, and the like).

In[1]:=
expr = (2*(B - b)^2 - 2*(A - a)*c*d^2)/(4*b^2*(1 - c*2)*d^2)

Out[1]=
           2                 2
2 (-b + B)  - 2 (-a + A) c d
-----------------------------
          2            2
       4 b  (1 - 2 c) d

In[2]:=
Numerator[expr]

Out[2]=
           2                 2
2 (-b + B)  - 2 (-a + A) c d

Regards,
Jean-Marc


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