MCQ
Evaluate $\begin{bmatrix}5&0&5\\1&4&3\\0&8&6\end{bmatrix}$ is:
  • A
    $20$
  • $0$
  • C
    $-40$
  • D
    $40$

Answer

Correct option: B.
$0$
$\triangle=\begin{bmatrix}5&0&5\\1&4&3\\0&8&6\end{bmatrix}$
Expanding along $\text{R}_1,$ we get:
$\triangle=5\begin{bmatrix}4&3\\8&6\end{bmatrix}-0\begin{bmatrix}1&3\\0&6\end{bmatrix}+5\begin{bmatrix}1&4\\0&8\end{bmatrix}$
$\triangle=5(24-24)-0+5(8-0)$
$\triangle=0-0+40=40.$

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