Let A be a 3 3 matrix and (A)=2. If n= ( 2024 times adj(adj( (adj A)))), then the remainder when n is divided by 9 is equal to .
Answer
7
Solution
For a 3 3 matrix: |adj A|=|A|2
applying adj 2024 times: n=|A|22024=222024
∵ 26=64 1 (mod 9), we need 22024 (mod 6)
22024=41012=(3+1)1012 1 (mod 3) and it is even 22024=6k+4
n=26k+4= (26 )k 16 16 7 (mod 9)
Answer: 7