If $A =\begin{bmatrix}5&6\\3&2\end{bmatrix}$ then which of the following is correct? (A) $|A|$ is positive Choose the correct answer from the options given below: |
(B) and (D) only (A), (B) and (C) only (A), (C) and (D) (C) and (D) only |
(B) and (D) only |
The correct answer is Option (1) → (B) and (D) only ** $A=\begin{bmatrix}5 & 6 \\ 3 & 2\end{bmatrix}$ Determinant: $|A| = 5\cdot2 - 6\cdot3 = 10 - 18 = -8$ (A) $|A|$ is positive → false (it is $-8$) (B) $|\text{adj}\,A| = -8$ For a $2\times2$ matrix: $|\text{adj}\,A| = |A|^{1} = -8$ → true (C) Cofactor of $3$: Cofactor of $3 = (-1)^{2+1}\cdot\text{minor} = -\left|\begin{matrix}6\end{matrix}\right| = -6$ → not $6$ → false (D) $|2A|$: $|2A| = 2^{2}|A| = 4(-8) = -32$ → true Correct statements: (B) and (D) |