If A is a square matrix of order 3 such that $|A|= 3$, then $|adj(adj\, A)|$ is equal to: |
1/3 3 6 81 |
81 |
The correct answer is Option (4) → 81 Given: $A$ is a $3 \times 3$ matrix and $|A| = 3$. For an $n \times n$ matrix: $|\text{adj}\,A| = |A|^{\,n-1}$ Since $n = 3$: $|\text{adj}\,A| = 3^{2} = 9$ Now apply the formula again to $\text{adj}\,A$ (which is also $3 \times 3$): $|\text{adj}(\text{adj}\,A)| = |\text{adj}\,A|^{\,n-1}$ $= 9^{2}$ $= 81$ Thus, $|\text{adj}(\text{adj}\,A)| = 81$. |