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MathGroup Archive 2001

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31319] Re: (-8)^(1/3)
  • From: "Angel E. Andreu" <aandreu at localnet.com>
  • Date: Sat, 27 Oct 2001 01:08:37 -0400 (EDT)
  • References: <9rb6rm$5ch$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Using Mathematica v.4:

When I enter (-8)^(1/3) I received:

2(-1)^(1/3)

Given that you wrote your Mathematica response as 1 + 1.73205i,
reminds one of solving the cubic equation: x³ + 8 = 0. Thus, here are
some commands that yield your desired result of -2:

In[1]:= Solve[x³ +8 = = 0] [[1]]
Out[1] {x -> -2}

or

In[2]:= Root[ #1^3 + 8&, 1]
Out[2] -2

A²


LuisMa wrote:

> When I enter
>
> (-8)^(1/3)
>
> Mathematica answer
>
> 1 + 1.73205i,
>
> but I need
>
> (-8)^(1/3) = -2
>
> How can I get it?

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