MCQ
For any $2-$rowed square matrix $A,$ if $A \cdot(\operatorname{adj} A)=\left[\begin{array}{ll}8 & 0 \\ 0 & 8\end{array}\right]$ then the value of $| A |$ is
  • $8$
  • B
    $4$
  • C
    $0$
  • D
    $64$

Answer

Correct option: A.
$8$
$(\operatorname{adj} A)=\left(\begin{array}{ll} 8 & 0 \\ 0 & 8 \end{array}\right) \\ =8\left(\begin{array}{ll} 1 & 0 \\0 & 1\end{array}\right) \\=|A| I \\|A|=8$

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