Three Excel functions are helpful with matrices: MMULT for matrix multiplication, MINVERSE for finding the inverse of the matrix, and MDETERM for finding the determinant of a matrix.

To multiply matrices in Excel, use MMULT as follows:

1. Highlight all the cells that will contain the resulting matrix.

2. Type = MMULT(matrix1, matrix2), where matrix1 and matrix2 are the cell ranges for the two matrices being multiplied.

3. Instead of just pressing Enter, press $\text{Ctrl}\text{+}\text{Shift}\text{+}\text{Enter}.$

Pressing $\text{Ctrl}\mathrm{+}\text{Shift}\mathrm{+}\text{Enter}$ simultaneously indicates that a matrix operation is being performed, so all cells in the matrix are changed accordingly. Program M5.1A provides an example of this in cells F9:G10. The output is shown in Program M5.1B.

The MINVERSE function is illustrated in cells F14:G15 of Program M5.1A. Remember that the entire range of the matrix (F14:G15) must be highlighted before entering the MINVERSE function. Pressing $\text{Ctrl}\mathrm{+}\text{Shift}\mathrm{+}\text{Enter}$ provides the final result shown in Program M5.1B.

The MDETERM function is used to find the determinant of a matrix. This is illustrated in cell F19 of Program M5.1A. The numerical result is shown in Program M5.1B.