# How do you know if a matrix does not have an inverse?

If the determinant of the matrix is zero, then it will not have an inverse; the matrix is then said to be singular. Only non-singular matrices have inverses. Find the inverse of the matrix A = ( 3 1 4 2 ). result should be the identity matrix I = ( 1 0 0 1 ).
A.

### What is the invertible matrix Theorem?

Invertible Matrix Theorem. The invertible matrix theorem is a theorem in linear algebra which gives a series of equivalent conditions for an square matrix to have an inverse. In particular, is invertible if and only if any (and hence, all) of the following hold: 1. The linear transformation is one-to-one.
• #### What is the rank of a matrix?

The maximum number of linearly independent vectors in a matrix is equal to the number of non-zero rows in its row echelon matrix. Therefore, to find the rank of a matrix, we simply transform the matrix to its row echelon form and count the number of non-zero rows.
• #### What does it mean for a matrix to be nonsingular?

A square matrix that is not singular, i.e., one that has a matrix inverse. Nonsingular matrices are sometimes also called regular matrices. A square matrix is nonsingular iff its determinant is nonzero (Lipschutz 1991, p. 45).
• #### When a matrix is not invertible?

A square matrix that is not invertible is called singular or degenerate. A square matrix is singular if and only if its determinant is 0. Singular matrices are rare in the sense that a square matrix randomly selected from a continuous uniform distribution on its entries will almost never be singular.

Updated: 28th October 2019