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If $A=\left[\begin{array}{ccc}1 & 0 & 2 \\ 2 & 1 & 3 \\ 0 & 3 & -5\end{array}\right]$, where $A_{\text {ij }}$ is the cofactor of the element $a_{\text {ij }}$ of matrix $A$, then
$a_{21} A_{21}+a_{22} A_{22}+a_{23} A_{23}=$
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$a_{21} A_{21}+a_{22} A_{22}+a_{23} A_{23}=$
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Verified Answer
The correct answer is:
$-2$
$\begin{aligned} a_{21} & A_{21}+a_{22} A_{22}+a_{23} A_{23} \\ &=-2(0-6)+1(-5-0)-3(3-0) \\ &=12-5-9=-2 \end{aligned}$
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