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MathGroup Archive 2002

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Re: How to find and plot real roots?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33573] Re: [mg33566] How to find and plot real roots?
  • From: BobHanlon at aol.com
  • Date: Mon, 1 Apr 2002 02:02:05 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 3/31/02 4:19:00 AM, anok at earthlink.net writes:

>How does one find the real root, for example:
>
>(-1)^(1/3) in Mathematica ?
>
>Also, I want to plot x^(1/3)*(x+3)^(2/3), but the fact that Mathematica
>doesn't 
>know which roots to pick causes errors in the Plot function.  How to force
>
>it to find real roots?
>

Select[Solve[x^3==-1,x], Element[x /. # , Reals]&]

{{x -> -1}}

-Abs[(-1)^(1/3)]

-1

Needs["Graphics`Colors`"];

Plot[Sign[x]*Abs[x^(1/3)*(x+3)^(2/3)],
 
    {x,-5,2}, 
PlotStyle->Red];


Bob Hanlon
Chantilly, VA  USA


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