You are correct, you did something "wrong".
You did not supply the right form for the argument expected by solve.
If you wish to set things up as a matrix, instead of a list of equations,
you could always convert by doing something like this:
s: m1.m2-m3; /* your example */
listofeqs: [s[1],s[2]];
listofvars: [x,y];
solve(listofeqs, listofvars);
if you don't know in advance the size of the matrices, you can
find them out and use listofeqs: makelist(s[i],i,1,length(s));
If you want to add this feature to solve,
you are welcome to look at the code and figure out how.
RJF
----- Original Message -----
From: "Via Purifico" <union at bluebottle.com>
To: <maxima at math.utexas.edu>
Sent: Wednesday, May 24, 2006 6:06 PM
Subject: solving equations involving matrices
> Hello, I am somewhat new to Maxima. I am trying to solve this simple
> system of linear equations:
>
> 3x + 8y = 5
> 4x + 11y = 7
>
> I put them into a matrix and tried to solve:
>
> (%i19) matrix([3,8],[4,11]) . matrix([x],[y]) = matrix([5],[7]);
>
> [ 8 y + 3 x ] [ 5 ]
> (%o19) [ ] = [ ]
> [ 11 y + 4 x ] [ 7 ]
> (%i20) solve(%,[x,y]);
>
> (%o20) []
>
> This somewhat disappointed me, because when I did:
>
> (%i18) solve([3*x + 8*y = 5, 4*x + 11*y = 7],[x,y]);
>
> (%o18) [[x = - 1, y = 1]]
>
> it seemed to work fine. Am I doing something wrong? Why doesn't Maxima
> have an answer for the equation involving matrices?
>
> _______________________________________________
> Maxima mailing list
> Maxima at math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
>