For example, the determinant of matrix A = 
1
2
4
8



  is zero
Hence A is a singular matrix Definition 5 A square matrix A is said to be non-singular if A  ≠ 0
Let
A = 
1
2
3
4





 Then A = 
1
2
3
4  = 4 – 6 = – 2 ≠ 0 Hence A is a nonsingular matrix
We state the following theorems without proof