What does 'write A as a product of 4 elementary matrices' mean?

In summary, to find the elementary matrices in this problem, you need to perform row operations on the identity matrix to get the desired result. This means swapping rows, multiplying every number in a row by the same number, or adding a multiple of one row to another. Only one elementary matrix is needed for this problem.
  • #1
LaraCroft
14
0

Homework Statement


So, if the problem asks...

Find the elementary matrices such that the respective matrix equation holds...what do I do?

[_ _ _] [4 4 -1] [4 4 -1 ]
[_ _ _] [4 -1 -5] = [4 -1 -5]
[_ _ _] [-4 1 4] [-12 3 12]

Does this mean to find a matrix that when multiplied with the other gives the matrix on the other side of the equal sign?


Homework Equations





The Attempt at a Solution

 
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  • #2
i think that is what it means..
 
  • #3
LaraCroft said:

Homework Statement


So, if the problem asks...

Find the elementary matrices such that the respective matrix equation holds...what do I do?

[_ _ _] [4 4 -1] [4 4 -1 ]
[_ _ _] [4 -1 -5] = [4 -1 -5]
[_ _ _] [-4 1 4] [-12 3 12]

Does this mean to find a matrix that when multiplied with the other gives the matrix on the other side of the equal sign?


Homework Equations





The Attempt at a Solution


This problem assumes that you know what an "elementary" matrix is!

An elementary matrix is one that corresponds to a "row operation". Multiplying any matrix by that elementary matrix is the same as doing the corresponding row operation to the matrix.

There are three kinds of row operations:
a) Swap two rows of the matrix.
b) Multiply every number in one row by the same number.
c) Add a multiple of one row to another.

You get the elementary operation corresponding to a row operation just by performing that row operation on the identity matrix.

What row operation will change the matrix on the left into the matrix on the right? Although your title says "4 elementary matrices", for this problem onlyone is required.
 

1. What are elementary matrices?

Elementary matrices are square matrices with a single non-zero entry in each row and column, and all other entries being zero. They are used in linear algebra to perform elementary row operations, such as swapping rows, multiplying rows by a scalar, and adding a multiple of one row to another.

2. What does it mean to write A as a product of elementary matrices?

Writing A as a product of elementary matrices means expressing matrix A as a combination of elementary matrices that, when multiplied together, result in the original matrix A. This is useful for performing matrix operations and simplifying calculations.

3. Why is it important to write A as a product of elementary matrices?

Writing A as a product of elementary matrices allows us to easily perform operations on the matrix, such as finding its inverse or calculating its determinant. It also helps to simplify complex matrices and make them easier to work with.

4. How do you write A as a product of elementary matrices?

To write A as a product of elementary matrices, you can use Gaussian elimination or row reduction to convert A into an identity matrix. The elementary matrices used in this process can then be multiplied together to form a product that results in A.

5. Can any matrix be written as a product of elementary matrices?

No, not all matrices can be written as a product of elementary matrices. This is because not all matrices can be reduced to an identity matrix using elementary row operations. However, most matrices encountered in linear algebra can be written as a product of elementary matrices.

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