HP 40G manual $/3+$@M1@ $/3+$@M2 175@, $/3+$@M1 j@$/3+$@M2 175@

To multiply two matrices

To divide by a square matrix

To invert a matrix

To negate each element

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.

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@

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@.

You can change the sign of each element in a matrix by pressing >￿￿￿@ before the matrix name.

Matrices 12-7