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MathGroup Archive 2001

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Re: (-8)^(1/3)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31299] Re: (-8)^(1/3)
  • From: "Steve Luttrell" <luttrell at signal.qinetiq.com>
  • Date: Sat, 27 Oct 2001 01:08:08 -0400 (EDT)
  • Organization: Defence Evaluation & Research Agency
  • References: <9rb6rm$5ch$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"LuisMa" <nospam at newsranger.com> wrote in message
news:9rb6rm$5ch$1 at smc.vnet.net...
> When I enter
> (-8)^(1/3)
> Mathematica answer
> 1 + 1.73205i,
> but I need
> (-8)^(1/3) = -2
> How can I get it?

If you evaluate this:

Solve[x^3 == -8, x]

then you get the following output:

{{x -> -2}, {x -> 2*(-1)^(1/3)}, {x -> -2*(-1)^(2/3)}}

You can then use this to replace x by whichever of the 3 roots that you
require.

--
Steve Luttrell
QinetiQ
Malvern Technology Centre
UK





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