Re: Solution of this equation

• To: mathgroup at smc.vnet.net
• Subject: [mg20663] Re: Solution of this equation
• From: "David Bailey" <db at salford-software.com>
• Date: Sun, 7 Nov 1999 02:10:02 -0500
• Organization: University of Salford, Salford, Manchester, UK
• References: <7vrc3p\$2nd@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Dave Richardson <dhr at glue.umd.edu> wrote in message
news:7vrc3p\$2nd at smc.vnet.net...
> Can anyone offer insight here?
>
> This Mathematica expression gives 3 solutions to the equation.
>
> Solve[Pr == (8*Tr)/(3*vr - 1) - 3/vr^2, vr]
>
>
> The problem is that there are 3 Real solutions, and Mathematica is giving
> solutions with (granted a small) imaginary component.
>
> And hitting it with  a full simplify is just not a good idea...
>
>
> Any help?

The problem is that you have a cubic equation if vr, and unless such an
equation factors (which your doesnt) you end up using the general cubic
solution which is usually of very little use because it is so complicated.
If you have numeric values for Tr and Pr it would make more sense to use
NSolve.

David Bailey
Salford Software

```

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