# If A is an invertible matrix of order 2, then det (A-1) is equal to

(a) det (A)

(b) 1/det(A)

(c) 1

(d) 0

Solution:

We know AA-1 = I

Take determinant on both sides

|AA-1| = |I|

|A| |A-1| = 1

=> |A-1| = 1/|A|

Hence option b is the answer.