HP 39g+ - Manual (Page 179)

Matrices 12-7
To multiply two
matrices To multiply the two matrices M1 and M2 that you created for
the previous example, use the following keystrokes:
>$/3+$@M1>[@ >$/3+$@M2
>(17(5@
To multiply a matrix by a vector, enter the matrix first, then
the vector. The number of elements in the vector must equal
the number of columns in the matrix.
To divide by a
square matrix For division of a matrix or a vector by a square matrix, the
number of rows of the dividend (or the number of elements, if
it is a vector) must equal the number of rows in the divisor.
This operation is not a mathematical division: it is a left–
multiplication by the inverse of the divisor. M1/M2 is
equivalent to M2
–1 * M1.
To divide the two matrices M1 and M2 that you created for the
previous example, use the following keystrokes:
>$/3+$@M1 >j@ >$/3+$@M2
>(17(5@
To invert a matrix You can invert a square matrix in HOME by typing the matrix
(or its variable name) and pressing
>6+,)7@x –1 >(17(5@. Or you
can use the matrix INVERSE command. Enter
INVERSE(matrixname) in HOME and press
>(17(5@.
To negate each
element You can change the sign of each element in a matrix by
pressing
>  @ before the matrix name.