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MathGroup Archive 2007

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Re: Plotting

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73000] Re: Plotting
  • From: Peter Pein <petsie at dordos.net>
  • Date: Sun, 28 Jan 2007 01:07:54 -0500 (EST)
  • References: <epfa83$doc$1@smc.vnet.net>

Rayne schrieb:
> Hi all,
> I want to plot the cubic equation f(x) == x^3 - 16x^2 + 3x + 1 == 0. I had:
> 
> f==x^3-16 x^2+3 x+1 ==== 0
> Plot[f,{x,-1,20}]
> 
> but I was unable to get the plot. The error message says
> 
> Plot::plnr: f is not a machine-size real number at x == -0.999999.
> Plot::plnr: f is not a machine-size real number at x == -0.148093.
> Plot::plnr: f is not a machine-size real number at x == 0.780985.
> General::stop: Further output of Plot::plnr
>      will be suppressed during this calculation.
> 
> How do I get around this problem?
> 
> Thank you.
> 
> Regards,
> Rayne
> 

Hi Rayne,

read about basic syntax issues in the help browser.

Didn't you realize the syntax error "f==x^3...===0 can not be followed by =0"?

My crystall ball fails terribly.

if you want f to be the root(s) of a polynomial, the value(s) will be
constants. And if you want to plot the values of a polynomial, what does the
"====0" mean. What do 4 "="s mean at all and why do you ask Mathematica if f
is equal to x^3-16x^2+3x+1====0? Where has f been defined? Why don't you care
about syntax errors?

I really do not understand what you want, sorry.


Peter

-- 
http://moratoriumcampaign.org/


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