How Do Row Operations Affect Matrix Determinants?

In summary, the determinant of a matrix is equal to the product of all its eigenvalues. In the first scenario, multiplying the third row by 8 results in the determinant of the new matrix B being multiplied by 8. In the second scenario, swapping the second and fourth rows does not change the determinant. Therefore, the determinant of matrix C remains the same.
  • #1
LaraCroft
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Homework Statement


If the determinant of a 3 x 3 matrix A is det(A) = 10, and the matrix B is obtained by multiplying the third row by 8, then det(B) = ___?

If the determinant of a 5 x 5 matrix A is det(A) = 9, and the matrix C is obtained from A by swapping the second and fourth rows, then det(C) =___?

Homework Equations



Ok, so do I use a generic matrix, or what? SO confused...

The Attempt at a Solution

 
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  • #2
Hi LaraCroft! :smile:

Useful tip: write out a few matrices (easy ones, with lots of zeros :wink:), and see what happens …

then you can set about proving why :smile:
 

1. What is a determinant?

A determinant is a mathematical concept that is used to describe certain properties of a square matrix. It is a numerical value that can be calculated from the elements of a matrix and is often used to solve systems of linear equations.

2. How do you calculate a determinant?

The specific method for calculating a determinant depends on the size of the matrix. For a 2x2 matrix, the determinant is simply the product of the elements on the main diagonal minus the product of the elements on the other diagonal. For larger matrices, there are various methods such as expansion by minors or using certain properties of determinants.

3. What is the significance of determinants in linear algebra?

Determinants are important in linear algebra because they can be used to solve systems of linear equations, find inverses of matrices, and determine linear independence of vectors. They also have applications in geometry and physics.

4. Can determinants be negative?

Yes, determinants can be negative. The value of a determinant can be positive, negative, or zero depending on the values of the elements in the matrix. A negative determinant indicates that the matrix is not invertible.

5. Are determinants only used for square matrices?

Yes, determinants are only defined for square matrices. This means that the number of rows and columns must be equal. For example, a 3x3 matrix has a determinant, but a 2x3 or 3x2 matrix does not.

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