Proving Singular Matrix A Has Nonzero Matrix B: Linear Algebra Problem

In summary, the conversation discusses proving that for every square singular matrix A, there is a nonzero matrix B such that AB equals the zero matrix. The individual has found a way to make AB equal the identity matrix, but not the zero matrix. The conversation then delves into the reasoning behind this and the use of determinants in proving the statement.
  • #1
Braka
5
0
The problem is prove that for every square singular matrix A there is a nonzero matrix B, such that AB equals the zero matrix.

I got AB to equal the idenity matrix, but have no clue how to get it to the zero matrix.
 
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  • #2
If A is viewed as the matrix of a linear transformation, then it being singular is the same as saying that it maps a subspace in the domain to the 0 subspace of the range. Find the kernel of A and let B be a matrix of vectors in that space.
 
  • #3
you said:
I got AB to equal the idenity matrix, but have no clue how to get it to the zero matrix.

how did you do that? If A is singular then it doesn't have an inverse, but you found one namely B.
 
  • #4
If A is singular, det(A)= 0. Also det(AB)= det(A)det(B). You, apparently, have proved that det(AB)= 0(det(B)= 0= det(I)= 1. A miracle indeed!
 

What is Linear Algebra?

Linear Algebra is a branch of mathematics that deals with linear equations, matrices, vectors, and their properties. It is used to solve problems in various fields such as physics, engineering, and computer science.

What are the main applications of Linear Algebra?

Linear Algebra has many applications in fields such as data analysis, computer graphics, optimization, and machine learning. It is also used in solving systems of equations, finding eigenvalues and eigenvectors, and performing transformations in geometry.

What is a matrix and how is it used in Linear Algebra?

A matrix is a rectangular array of numbers or symbols. In Linear Algebra, matrices are used to represent linear transformations and solve systems of linear equations. They are also used to perform operations such as addition, subtraction, multiplication, and inversion.

What is a vector and how is it related to Linear Algebra?

A vector is a mathematical object that has magnitude and direction. In Linear Algebra, vectors are used to represent quantities that have both magnitude and direction, such as velocity and force. They can also be used to represent points in space and perform operations such as addition, subtraction, and scalar multiplication.

What are eigenvalues and eigenvectors?

Eigenvalues and eigenvectors are important concepts in Linear Algebra. Eigenvalues are the values that satisfy the equation Av = λv, where A is a square matrix, v is a vector, and λ is a scalar. Eigenvectors are the corresponding vectors that are scaled by the eigenvalue λ. They are used in many applications such as solving systems of differential equations and diagonalizing matrices.

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