Matrix multiplication expansion

Hello Fr?d?ric,

> (%i1) A1:Matrix([a,b,c],[d,e,f],[g,h,i]);
>
> (%o1)               Matrix([a, b, c], [d, e, f], [g, h, i])

Maxima is now (since 5.9.2) case sensitive.
That is, Matrix, MATRIX, and matrix are all different symbols.
You want matrix (minuscule letters) here.

Hope this helps,
Robert Dodier