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MathGroup Archive 2001

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Re: Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32029] Re: [mg32007] Simplify
  • From: BobHanlon at aol.com
  • Date: Wed, 19 Dec 2001 04:29:10 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 12/18/01 2:59:34 AM, Matthias.Bode at oppenheim.de writes:

>why should I not expect MATHEMATICA to (Full)Simplify
>
>(a^b)^(1/b) or a^b^(1/b) to a?

Counter-example:

((-.7-.3I)^2.1)^(1/2.1)

0.7368942582104423 + 0.19231966154421648*I

(a^b)^(1/b) // PowerExpand

a

(a^(1/b))^b // PowerExpand

a

PowerExpand are correct in general only if c is an integer or a and b are 
positive real numbers."

Simplify[(a^(1/b))^b, Element[{a,b}, Reals]&&a>0&&b>0]

a

Simplify[(a^b)^(1/b), Element[{a,b}, Reals]&&a>0&&b>0]

a

Simplify[(a^(1/b))^b, Element[b, Integers]]

a


Bob Hanlon
Chantilly, VA  USA


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