This is fairly hard in general, but in this case with suitable assumptions:
Take the logarithm reassigning the independent variables
a1=log(a), x1=log(x) etc..... Then it's linear and you can formulate
general solutions.
R.Rogers
> From: Park Hays [mailto:park at thistlebear.net]
>
>
> I did not search the archive (not really searchable is
> it?)--so if this
> is a common question please sling mud at will.
>
> I'm new to maxima, but encountered a similar point in Mathcad
> recently.
> Very simple equation/function
>
> f(x) = a*x^-b;
> I have two data points, e.g.,
> f( 5e9) = 290; f( 1e8)=3e6;
> This is easily solved with some logarithms...but not with
> solve(). For
> example:
> (%i1) solve( [290 = a*5e9^-b, 3e8=a*1e8^-b],[a,b]);
>
> RAT replaced 3.0E+8 by 300000000//1 = 3.0E+8
> (%o1) []
>
> Any hints? Is this general sort of problem beyond symbolic solver's
> capabilities?
>
> Yours,
> Park
>
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