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Re: Problems with Solve

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Newsgroups comp.soft-sys.math.mathematica
Subject Re: Problems with Solve
Date Sun, 30 Mar 2014 08:42:28 +0000 (UTC)
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On Sun, 23 Mar 2014 08:59:35 +0000, Ray Koopman wrote:

> 1. Use  NRoots[z + 5 (z^2 - 1) + 1 z^3 == 1, z], then pick the root you
> want.
> 
> 2. B[s_?NumericQ] := Piecewise[{{Erfc[-x]+Erfc[y]-Erfc[z], s >= .5}},
> Erfc[-x]]
> 
> ----- Samuel Mark Young <sy81@sussex.ac.uk> wrote:
>> I'm trying to use the solutions of Solve from solving a cubic equation
>> - however, it keeps returning complex answers when there are real
>> solutions. For example:
>> 
>> Solve[z + 5 (z^2 - 1) + 1 z^3 == 1, z]
>> 
>> This equation has 3 real solutions. However, the answers returned when
>> I ask mathematica for a decimal answer are complex... 
  
Wow, I manually entered <1> to the rPi <creditCardSized computer>.
Amazing: but where's the syntax [without TOO much commercials] for my
free version of mathematica?

Why did the OP use "Solve"?
And how did the look-ma-no-hands-demo respondent [whithout any 
elaboration/explanation to add value] know to use a different syntax?
And, within the context of <solutions of cubic equations>, what is
the meaning of "== 1, z"?

== TIA.

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Re: Problems with Solve Ray Koopman <koopman@sfu.ca> - 2014-03-23 08:59 +0000
  Re: Problems with Solve Unknown <dog@gmail.com> - 2014-03-30 08:42 +0000

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