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Re: N::meprec warning with Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86749] Re: [mg86696] N::meprec warning with Solve
  • From: Curtis Osterhoudt <cfo at lanl.gov>
  • Date: Thu, 20 Mar 2008 02:53:23 -0500 (EST)
  • Organization: LANL
  • References: <200803191021.FAA04722@smc.vnet.net>
  • Reply-to: cfo at lanl.gov

Hi, Peter, 

   At least on my system ( 6.0.1.0 on 32-bit Linux), the result of the Solve 
command is as follows (no application of N apparent): 

{{x -> -(1/4) - (1/2)*Sqrt[-(5/12) + 
               61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
               (1/3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)] - 
         (1/4)*
     Sqrt[(1/3)*(-10 - 244/((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3) - 
                  2*2^(2/3)*(-223 + 9*I*Sqrt[10595])^(1/3) - 
                  
         9/Sqrt[-(5/12) + 
            61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
                        (1/
               3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)])]}, 
   {x -> -(1/4) - (1/2)*Sqrt[-(5/12) + 
               61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
               (1/3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)] + 
         (1/4)*
     Sqrt[(1/3)*(-10 - 244/((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3) - 
                  2*2^(2/3)*(-223 + 9*I*Sqrt[10595])^(1/3) - 
                  
         9/Sqrt[-(5/12) + 
            61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
                        (1/
               3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)])]}, 
   {x -> -(1/4) + (1/2)*Sqrt[-(5/12) + 
               61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
               (1/3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)] - 
         (1/4)*
     Sqrt[(1/3)*(-10 - 244/((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3) - 
                  2*2^(2/3)*(-223 + 9*I*Sqrt[10595])^(1/3) + 
                  
         9/Sqrt[-(5/12) + 
            61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
                        (1/
               3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)])]}, 
   {x -> -(1/4) + (1/2)*Sqrt[-(5/12) + 
               61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
               (1/3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)] + 
         (1/4)*
     Sqrt[(1/3)*(-10 - 244/((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3) - 
                  2*2^(2/3)*(-223 + 9*I*Sqrt[10595])^(1/3) + 
                  
         9/Sqrt[-(5/12) + 
            61/(3*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)) + 
                        (1/
               3)*((1/2)*(-223 + 9*I*Sqrt[10595]))^(1/3)])]}}


    Hope that helps!
                C.O.

On Wednesday 19 March 2008 04:21:27 Peter Breitfeld wrote:
> consider the function:
>
> f[x_] := (x^4 + x^3 + x^2 + 5)/(5 x^2 + 5 x + 5)
>
> lsg=Solve[f[x]==0,x]
>
> gives the warnings:
>
> N::meprec:
> "Internal precision limit $MaxExtraPrecision = 50.` reached while
> evaluating Im[61/(3\(<<1>> <<1>>)^(1/3))+1/3\ (1/2\(<<1>>))^(1/3)]."
>
> How can this happen if no Reals are used? Why is N called?
>
> BTW the results of Solve are correct
>
> Gruss Peter



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