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From: d0mo@dtek.chalmers.se (Mats Olsson)
Newsgroups: comp.sys.handhelds
Subject: Re: How do I row reduce matrices on a 48?
Message-ID: <1991Feb14.133413.12634@mathrt0.math.chalmers.se>
Date: 14 Feb 91 13:34:13 GMT
References: <A9043F8720000431@gacvx2.gac.edu>
Sender: news@mathrt0.math.chalmers.se (Evald Nyhetsson)
Organization: Dep of Mathematics, Chalmers, Gothenburg
Lines: 38

>Actually Matt you're not missing it in the manuals.  HP did not include
>this feature in the calcualtor since I believe its only use is in solving
>multivariable linear equations.  This is much more easily accomplished
>on the HP by the following method:
...
>Then press the divide key and the answers are on the stack in the form:
-----

The method described above does only work for quadratic systems of equations.

Consider a system of equations with n unknowns and m equations.
In matrix form the system reads:

           Ax=b

where A is the coefficient matrix, type m*n, x is a vector containing
the unknowns, type m*1, and b is a vector containing the constants on
the right sides of the equations, also of type m*1.

If the solution of this system of equations is determined by
          
        x=b/A,

the matrix A have to be inversable and therefore quadratic.

<=> m=n 
<=> The system of equations is quadratic.


To solve a un-quadratic system of linear equations, one have to 
reduce the matrix into echelon form. This is easily done by my
program ->RED which I will post here very soon.. 

Be patient!!

Mats Olsson
Chalmers University of technology
Sweden