Matrices
Defining a matrix
Row operations
  Matrix operations
Row-echelon form (not available on the TI-82)
 Reduced row-echelon form (not available on the TI-82)




Defining a matrix
 
Press MATRX, and select EDIT (using the right arrow)
ENTER, 2, ENTER, 3, ENTER to define the dimensions of your matrix
Enter each matrix element.  After typing each element, press ENTER.
This defines the matrix [A].  



Row operations

We will do a series of elementary row operations on the matrix [A] defined above to place it in row-echelon form (by forward elimination) and then reduced row-echelon form (by backward elimination).  We assume [A] has already been defined, as shown above.
 

Forward Elimination  
MATRIX
Row operation
Get a 1 in upper left-hand corner byR1ßà R2
 
Select MATH (right arrow), then select rowSwap (down arrow to #8).
ENTER, then MATRX, ENTER (to select matrix [A])
, 1, 2) ENTER

You now see matrix [A] with its rows swapped.

Save (store) this matrix (as [A]) to prepare for the next operation. 

STO MATRX ENTER ENTER

Row operation
Make the 3 a 0 by -3R1 + R2à R2
 
MATRIX, select MATH, select *row+ (#A), ENTER
-3, MATRX ENTER,1,2)
STO MATRX ENTER ENTER
Row operation
Make the 10 a 1 by (1/10)R2à R2
 
MATRX, select MATH, select *row, ENTER
.1, MATRX ENTER , 2) ENTER 
STO MATRX ENTER ENTER
The matrix is now in row-echelon form.  
   
Backward Elimination  
Row operation
Make the -2 (in row 1) a 1 by 2R2 + R1à R1
 
MATRX, select MATH, select *row+, ENTER
2, MATRX ENTER , 2, 1) ENTER 
STO MATRX ENTER ENTER
The matrix is now in reduced row-echelon form, and the answer is: x = 3, y = -2