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# If a is a Square Matrix Such that a ( a D J a ) = ⎡ ⎢ ⎣ 5 0 0 0 5 0 0 0 5 ⎤ ⎥ ⎦ , Then Write the Value of |Adj A|. - CBSE (Arts) Class 12 - Mathematics

ConceptDeterminant of a Square Matrix

#### Question

If A is a square matrix such that $A \left( adj A \right) = \begin{bmatrix}5 & 0 & 0 \\ 0 & 5 & 0 \\ 0 & 0 & 5\end{bmatrix}$ , then write the value of |adj A|.

#### Solution

$\text{ Given: }\hspace{0.167em} A\left( adj A \right) = \begin{bmatrix} 5 & 0 & 0\\0 & 5 & 0\\0 & 0 & 5 \end{bmatrix}$
$\Rightarrow \hspace{0.167em} \left| A \right| I_n = 5\begin{bmatrix} 1 & 0 & 0\\0 & 1 & 0\\0 & 0 & 1 \end{bmatrix}$
$\Rightarrow \hspace{0.167em} \left| A \right| = 5$
$\text{Now,}\left| adj A \right| = \hspace{0.167em} \left| A \right|^{n - 1} = 5^{3 - 1} = 25$

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Solution If a is a Square Matrix Such that a ( a D J a ) = ⎡ ⎢ ⎣ 5 0 0 0 5 0 0 0 5 ⎤ ⎥ ⎦ , Then Write the Value of |Adj A|. Concept: Determinant of a Square Matrix.
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