# Matrix Operations on the TI-89

**Entering a Matrix: **Press [APPS] and select [Data/Matrix Editor].
Select either 1:Current, 2:Open..., or 3, New where appropriate.

Selecting New and entering the information about the matrix as follows:

Press [HOME] to return to the Home screen. Now pressing a and [ENTER] will show you the matrix.

** Row Operations :** The Row operations can be found by pressing [2^{nd}][MATH]
selecting [4: Matrix] and selecting [J: Row ops]. Row

ops is far enough down the list that moving up the list is faster. Here are
examples of row operations :

**Note:** If you are doing many row operations on the
same matrix you should use [ANS] instead of the name of the matrix after the
first

row operation .

**Row Echelon Form (ref) and Reduced Row Echelon Form
(rref):** Press [2

^{nd}][MATH] select [4:Matrix]. Select the

desired form followed by the name of the matrix and press

enter. For example:

**Inverse Matrices:** Select the name of the matrix and
raise it

to the –1 power . The matrix A above is not invertible so we

consider

If you want your results in fractions select
[Exact/Approx] after pressing [MODE]. Set the calculator to [2: EXACT] then all

computations will come out in fractions .

** Addition and Multiplication : **These operations are
done with the regular multiplication and addition keys along with the names of

the matrices. For example consider the matrices B and C shown on the left with
the computations shown on the right.

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