1  Determinant of a matrix of order one
Let A = [a] be the matrix of order 1, then determinant of A is defined to be equal to a
4 2 2  Determinant of a matrix of order two
Let
A = 
11
12
21
22
a
a
a
a






 be a matrix of order 2 × 2,
then the determinant of A is defined as:
det (A) = |A| = ∆ = 
 = a11a22 – a21a12
Example 1 Evaluate 
2
4
–1
2 Solution We have 
2
4
–1
2  = 2(2) – 4(–1) = 4 + 4 = 8