Why is another row operation necessary to obtain the matrix on the second line?

In summary, the 3x3 matrix at the right in the top line is not in reduced row-echelon form and the matrix at the right in the bottom line is almost in row-echelon form. To get it in row-echelon form, swap the first two rows, then swap the 2nd and 3rd rows. The definitions for row-echelon form and reduced row-echelon form were also provided. It is noted that the desired result could have been achieved in one step by adding 1 times the 3rd row to the first row.
  • #1
mathmathmad
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Homework Statement



[PLAIN]http://img260.imageshack.us/img260/727/picture2mg.png

just wondering.. isn't the the matrix on the 1st line already in its reduced row echelon form?
why is another row operation required to obtain the matrix on the 2nd line? (notice the changes to the matrix on the right)

Homework Equations


The Attempt at a Solution

 
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  • #2
I don't know what you're trying to do in this problem, but I'll answer your questions. The 3x3 matrix at the right in the top line is NOT in reduced row-echelon form. The matrix at the right in the bottom line is almost in row-echelon form (but not reduced row-echelon form). To get it in row-echelon form, swap the first two rows, then swap the 2nd and 3rd rows.

I think these are the definitions.
Row-echelon form: for each row with a non-zero leading entry, every other row below it has a 0 in that position.
Reduced row-echelon form: same as above, but also every other row above it has a 0 in that position.

Also, you could have done what you did in one step: Add 1 times the 3rd row to the first row.
 

What is reduced row echelon form?

Reduced row echelon form is a special form of a matrix where all the leading coefficients are 1 and all the other entries in the same column are 0. It is also known as row canonical form or reduced row-echelon matrix.

Why is reduced row echelon form important?

Reduced row echelon form is important because it allows us to easily solve systems of linear equations and to find the inverse of a matrix.

How do you find the reduced row echelon form of a matrix?

The reduced row echelon form of a matrix can be found by using elementary row operations such as multiplying a row by a non-zero scalar, swapping two rows, or adding a multiple of one row to another row.

What is the difference between row echelon form and reduced row echelon form?

In row echelon form, the leading coefficient of each row is 1, but there are no restrictions on the other entries in the same column. In reduced row echelon form, all the other entries in the same column must be 0.

Can every matrix be reduced to reduced row echelon form?

Not every matrix can be reduced to reduced row echelon form. A matrix is only reducible if it is a square matrix or has more rows than columns. Additionally, it may not be possible to reduce a matrix if there are no leading coefficients in a column or if there are infinitely many solutions to the system of equations represented by the matrix.

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