Minor of an element aij is
denoted by Mij Remark Minor of an element of a determinant of order n(n ≥ 2) is a determinant of
order n – 1 Example 8 Find the minor of element 6 in the determinant 
1
2
3
4
5
6
7
8
9
∆ =
Solution Since 6 lies in the second row and third column, its minor M23 is given by
M23 =
1
2
7
8  = 8 – 14 = – 6 (obtained by deleting R2 and C3 in ∆) Definition 2 Cofactor of an element aij, denoted by Aij is defined by
Aij = (–1)i + j Mij, where Mij is minor of aij