Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Matrices

Question:

If $A (adj\, A)= \begin{bmatrix}-5&0&0\\0&-5&0\\0&0&-5\end{bmatrix}$, then the value of $|A|$ is

Options:

-125

-5

5

125

Correct Answer:

-5

Explanation:

$A (adj\, A)=|A|I$

as $A (adj\, A)=\begin{bmatrix}-5&0&0\\0&-5&0\\0&0&-5\end{bmatrix}=-5\begin{bmatrix}1&0&0\\0&1&0\\0&0&1\end{bmatrix}$

$⇒|A|=-5$