Non-singular

In fact, it is worse than that. Many N × N matrices do not have an inverse. A matrix that does have an inverse is called non-singular. A matrix that does not is called singular. If the matrix A is non-singular, then:

AA^-1 = A^-1A = I

A non-singular matrix has a corresponding inverse. A singular matrix is all alone; it has no inverse.

Here is a matrix that has an inverse:

A			A-1			=	I
	1 2 0 1			1 -2 0 1		=		1 0 0 1
A-1			A			=	I
	1 -2 0 1			1 2 0 1		=		1 0 0 1

Now, say that

1 2 0 1

p =

5 2