Cofactors( Minors with Signs)
Cofactor of an element aij, denoted by Aij is defined by Aij =(– 1) i + j Mij, where
Mij is minor of aij.
Determinant = a11 A11 + a12 A12 + a13 A13 If elements of a row( or column) are multiplied with cofactors of any other row( or column), then their sum is zero
a11 A21 + a12 A22 + a13 A23 = 0 a11 A31 + a12 A32 + a13 A33 = 0
Ad joint of a Matrix( Cofactor- > Transpose)