Question

If $A=\left[\begin{array}{ccc}1& 2& -1\\ -1& 1& 2\\ 2& -1& 1\end{array}\right]$ then det (adj(adjA)) is

• A. $(14{)}^1$
• B. $(14{)}^2$
• C. $(14{)}^3$
• D. $(14{)}^4$

Answer 1

The correct option is D $(14{)}^4$

$|\text{adj(adj A)}|=|A{|}^{(n-1{)}^2}=(14{)}^4$