| Press MATRX, select EDIT (F2), The "A" seen under the cursor indicates that alphabetic mode is on. | |
| Name your matrix: A | |
| ENTER | |
| Define the dimensions of the matrix.
2 ENTER 3 ENTER |
|
| Enter each matrix element. After typing each element, press ENTER. | |
| This defines the matrix [A]. QUIT to return to the home screen. |
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 | |
| To see our matrix A:
MATRX, select EDIT (F2), A ENTER |
|
| Go to matrix operations:
QUIT MATRX select OPS (F4) |
|
| Row operation:
Get a 1 in upper left-hand corner byR1ßà R2 |
|
| MORE to move the menu to the right, then select rSwap (F2) | |
| select matrix A:
select NAMES (M1) and A (F1) |
|
| , 1, 2) ENTER
You now see matrix A with its rows swapped. |
|
| Save (store) this matrix back in A to prepare for the next operation.
STO A ENTER |
|
| Row operation:
Make the 3 a 0 by -3R1 + R2à R2 |
|
| select OPS (M4), select mRAdd (F5) | |
| -3, select NAMES (M1)
select A (F1)
, 1, 2) ENTER |
|
| STO A ENTER | |
| Row operation:
Make the 10 a 1 by (1/10)R2à R2 |
|
| select OPS (M4), select multR (MOREF4)
.1, ALPHA A, 2) ENTER STO A 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 |
|
| select OPS (M4), select mRAdd (MORE F5)
2, ALPHA A, 2, 1) STO A ENTER |
|
| The matrix is now in reduced row-echelon form, and the answer is: x = 3, y = -2 |
This operation performs forward elimination (see Row
operations, above) on a matrix in one step.
| Set FLOAT mode to 3 decimal places of precision:
MODE down arrow to select FLOAT, right arrow to select 3, ENTER |
|
| We start with the same matrix A as above (now with 0's as specified
in step 1):
ALPHA A ENTER |
|
| Go to matrix ops
MATRX F4 |
|
| Select "ref", specify A
F4 ALPHA A ENTER |
|
| Our matrix is now in row-echelon form. Note that it is not the same as obtained when we did the reduction steps by hand above. This is because row-echelon form is not unique. |
This operation does forward and backward elimination (see Row
operations, above) in one step.
| Starting with matrix A (see Row-echelon form for
setting precision).
ALPHA A ENTER |
|
| Go to matrix ops
MATRX F4 |
|
| Select "rref", specify A
F5 ALPHA A ENTER |
|
| Our matrix is now in reduced row-echelon form. Notice that this formis the same as found when we did the steps one by one. |