Linear Algebra - Matrix Multiplication

In summary, to find a 3x3 matrix B that satisfies AB = BA, one option is to create a diagonal matrix and multiply it by A. Another option is to use the inverse of A, A-1, which has the property that AA-1 = A-1A. To find the inverse of a matrix, you can use various methods such as Gaussian elimination or finding the adjugate matrix.
  • #1
jofree87
38
0
| 1 1 1 | = matrix A
| 1 2 3 |
| 1 4 5 |

How do I find a 3x3 matrix B, excluding the identity or zero matrix, such that AB = BA?
 
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  • #2
I think if you create and multiply by a diagonal matrix, it would work.
I know for sure that if A and B are diagonal matrices, AB=BA
 
  • #3
You could make a matrix of entries a b c d e f g h i and let that be matrix B,and you can then multiply AB and BA, and equate each entry or make a system of equations out of it and find what value each letter has in terms of the other letters. There may be an easier way I'm tired.
 
  • #4
jofree87 said:
| 1 1 1 | = matrix A
| 1 2 3 |
| 1 4 5 |

How do I find a 3x3 matrix B, excluding the identity or zero matrix, such that AB = BA?
The inverse of A, A-1, is a matrix for which AA-1 = A-1A. Do you know how to find the inverse of a given matrix?
 

1. What is matrix multiplication?

Matrix multiplication is a mathematical operation that combines two matrices to produce a third matrix. It is a fundamental concept in linear algebra and is used to represent linear transformations and solve systems of linear equations.

2. How do you perform matrix multiplication?

To perform matrix multiplication, you must first ensure that the number of columns in the first matrix is equal to the number of rows in the second matrix. Then, multiply each element in a row of the first matrix by each element in a column of the second matrix, and add the products together to get the corresponding element in the resulting matrix.

3. What is the significance of matrix multiplication?

Matrix multiplication is significant in various fields such as physics, engineering, computer science, and economics. It is used to represent linear transformations, solve systems of linear equations, and perform operations on data sets in statistics and machine learning.

4. What are some properties of matrix multiplication?

Matrix multiplication is associative, meaning that the order in which matrices are multiplied does not affect the result. It is also distributive, meaning that matrices can be multiplied by a scalar and then added. However, it is not commutative, meaning that the order of multiplication matters.

5. What are some common mistakes when performing matrix multiplication?

Some common mistakes when performing matrix multiplication include forgetting to check for the compatibility of matrix dimensions, mixing up the order of multiplication, and making computational errors. It is important to carefully check the dimensions and double-check the calculations to avoid these mistakes.

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