Sorry, I guess I made the assumption that solve was very smart and could
solve anything that all of Maxima itself could solve. I realize now that
solve isn't that clever and works best with algebraic equations.
And one small correction, s:m1.m2-m3; returns a matrix so
listofeqs:[s[1],s[2]]; returns a list of rows, not a list of equations
or expressions, so solve still wouldn't give any solutions.
listofeqs:[s[1][1],s[2][1]]; works fine on the other hand. I'm sure you
already knew this, however.
Thanks for your help.
Richard Fateman wrote:
> 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?
>>
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>>
>
>