page 1 of 2

We can perform three elementary row operations on matrices:

- Multiplying a row by a constant.
- Switching two rows.
- Adding a constant times a row to another row.

*Examples*:

- Multiplying a row by a constant:

- Switching two rows:

- Adding a constant times a row to another row:

We perform row operations to row reduce a matrix; that is, to
convert the matrix into a matrix where the first
*m*×*m*
entries
form the identity matrix:

where * represents any number.

This form is called reduced row-echelon form.

*Note:* Reduced row-echelon form does not always produce the
identity matrix, as you will learn in higher algebra. For our purposes,
however, we will consider reduced row-echelon form as only the form in
which the first
*m*×*m*
entries form the
identity matrix.

To row reduce a matrix:

- Perform elementary row operations to yield a "1" in the first row, first column.
- Create zeros in all the rows of the first column except the first row by adding the first row times a constant to each other row.
- Perform elementary row operations to yield a "1" in the second row, second column.
- Create zeros in all the rows of the second column except the second row by adding the second row times a constant to each other row.
- Perform elementary row operations to yield a "1" in the third row, third column.
- Create zeros in all the rows of the third column except the third row by adding the third row times a constant to each other row.
- Continue this process until the first
*m*×*m*entries form the identity matrix.

Take a Study Break!