Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section A

Chapter

Matrices

Question:

If the matrix $A=\begin{bmatrix} 1 & -1 & 2\\3 & 1 & -2 \\1 & 0 & 3\end{bmatrix}$, the value of |adj A| is :

Options:

134

144

12

121

Correct Answer:

144

Explanation:

The correct answer is Option (2) → 144

$|A|=\begin{vmatrix} 1 & -1 & 2\\3 & 1 & -2 \\1 & 0 & 3\end{vmatrix}$

$C_3→C_3-3C_1$

$\begin{vmatrix} 1 & -1 & -1\\3 & 1 & -11\\1 & 0 & 0\end{vmatrix}$

$=11+1=12$

so $|Adj\,A|=|A|^{n-1}=|A|^{3-1}=12^2$

$=144$