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Re: Simplify

• To: mathgroup at smc.vnet.net
• Subject: [mg32657] Re: Simplify
• From: "David P. Johnson" <johnson at nmtx.edu>
• Date: Sat, 2 Feb 2002 01:19:32 -0500 (EST)
• Organization: New Mexico Tech
• References: <a3f0q2$b3p$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

In article <a3f0q2$b3p$1 at smc.vnet.net>, Stich Sebastian
<seb_stich at gmx.ch> wrote:

> Hello
> 
> How can I simplify the following term?
> 
> (a^(1/3) - b^(1/3)) * ((a^(2/3) + (ab)^(1/3) + b^(2/3))/(a-b))^(1/3)
> 
> If I use the commands "Simplify", "FullSimplify", "Expand" or "PowerExpand"
> mathematica doesn't find the solution.
> The solution is (a^(1/3)-b^(1/3))^(2/3)
> If it's possible to find the solution in mathematica could mathematica show
> me the way this solution?
> 
> Thanks for your answers!

Well, you could learn some algebra. 

The quantity (a^(1/3)-b^(1/3)) does not equal (a-b)^(1/3), so you can't
cancel them. And didn't you mean ((a^(2/3) - 2(a*b)^(1/3) + b^(2/3))?
Even if you did, you can't change that to ((a^2 - 2(a*b) + b^2)^(1/3),
so you can't factor the expression inside the second parentheses. Your
proposed simplification is complete garbage. No wonder Simplify[]
didn't come up with it.

-- 
-David
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