Question

For any matrix A of order 2 × 2, if A(adj A) = [(10, 0), (0, 10)], then |A| is equal to

(A) 20

(B) 100

(C) 10

(D) 0

Answer 1

Answer is (C) 10

A (adj A) = [(10, 0), (0, 10)] = 10[(1, 0), (0, 1)] =10I.

Also A(adj A) = |A|I.

Hence, |A| = 10