II. Menu Keys - Keys that offer choices

E. MATRX (matrix) Menu

The matrix menu is quite extensive and an exhaustive study is beyond the scope of this tutorial. However, once you have learned what is presented here, you should have enough basic knowledge to use the remainder of the menu. The primary use of matrices in algebra is to solve a system of equations. The TI-86 has a function called SIMULT that will solve a system of linear equations. However, there are systems that have no solution and those that have infinite solutions. For systems such as these, the matrix menu is useful.

1. NAMES lists all the current matrices that are stored in the calculator. You can select a matrix from this menu to perform matrix operations.

2. EDIT is where you create a matrix. When you access this function, the calculator comes up in ALPHA format. In this menu you can also insert a row (INSr), delete a row (DELr), insert a column (INSc), and delete a column (DELc).

3. MATH is the menu to use when finding a determinant (det), transpose, etc.

4. OPS (operations) is the menu to use to perform row operations and to reduce a matrix to reduced row echelon form.

EXAMPLE: Solve the system using a matrix.

Press .
Type the name LSU.
Use the cursor
to set the size.
Press .
Enter the values.

Clear the screen
.

Press
.
Press
.

The solution is x=2, x=-1, x=4.

Example: Show that this system has no solution.

Create a 3X4
matrix as above.
Enter values.
Clear the screen
.
Press
.
Press
.
Put in fraction
form to see
the entire matrix.

The last row says that 0=1, which is false, so the system has no solution.