RE: Re: Help to solve numerical equation
- To: mathgroup at smc.vnet.net
- Subject: [mg43786] RE: [mg43753] Re: Help to solve numerical equation
- From: "David Park" <djmp at earthlink.net>
- Date: Sat, 4 Oct 2003 02:05:05 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Jean-Claude,
If you can narrow down the domain to a reasonable value then Ted Ersek's
RootSearch package from MathSource will get both roots.
Needs["Enhancements`RootSearch`"]
?RootSearch
RootSearch[lhs==rhs,{x,xmin,xmax}] tries to find all numerical solutions to
\
the equation (lhs==rhs) with values of x between xmin and xmax.
eq = 0.5*Exp[x*200] + 0.21*Exp[x*500] +
0.1*Exp[x*110] + 0.07*Exp[x*(15)] +
0.018*Exp[x*(-16)] + 0.002*Exp[x*(-263)] - 1;
RootSearch[eq == 0, {x, -1, 1}]
{{x -> -0.0232796}, {x -> 0.00042907}}
Plot[eq, {x, -0.03, 0.004}]
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: Jean-Claude Poujade [mailto:poujadej at yahoo.fr]
To: mathgroup at smc.vnet.net
bobhanlon at aol.com (Bob Hanlon) wrote in message
news:<blgiif$feh$1 at smc.vnet.net>...
> NSolve is used primarily with polynomial equations. Use FindRoot.
>
> eq=0.5*Exp[x*200]+0.21*Exp[x*500]+
> 0.1*Exp[x*110]+0.07*Exp[x*(15)]+
> 0.018*Exp[x*(-16)]+0.002*Exp[x*(-263)]-1;
>
> FindRoot[eq==0,{x,.0004}]
>
> {x -> 0.00042907}
>
>
> Bob Hanlon
Right! But FindRoot doesn't "see" there's another root...
---
jcp