# Thread: Show that a matrix ISNT invertible?

1. ## Show that a matrix ISNT invertible?

So matrix A is

1 2 1 0
3 1 2 3
2 5 0 1
2 -1 1 3

how will i go able showing that this matrix ISNT invertible?

2. ## Re: Show that a matrix ISNT invertible?

Originally Posted by Brennox
So matrix A is

1 2 1 0
3 1 2 3
2 5 0 1
2 -1 1 3

how will i go able showing that this matrix ISNT invertible?
A square matrix \displaystyle \begin{align*} \mathbf{A} \end{align*} is only invertible if \displaystyle \begin{align*} |\mathbf{A}| \neq 0 \end{align*}, so to show that this matrix is NOT invertible, evaluate \displaystyle \begin{align*} |\mathbf{A}| \end{align*} and show that it equals 0.