Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

Match List-I with List-II

List-I (Matrix A)

List-II (Determinant of adj A)

(A) $\begin{bmatrix}2&1\\0&-1
\end{bmatrix}$

(I) 6

(B) $\begin{bmatrix}0&1\\4&-1
\end{bmatrix}$

(II) 5

(C) $\begin{bmatrix}1&2\\-3&-1
\end{bmatrix}$

(III) -4

(D) $\begin{bmatrix}4&-2\\3&0
\end{bmatrix}$

(IV) - 2

Choose the correct answer from the options given below:

Options:

(A)-(IV), (B)-(III), (C)-(I), (D)-(II)

(A)-(I), (B)-(II), (C)-(IV), (D)-(III)

(A)-(III), (B)-(IV), (C)-(I), (D)-(II)

(A)-(IV), (B)-(III), (C)-(II), (D)-(I)

Correct Answer:

(A)-(IV), (B)-(III), (C)-(II), (D)-(I)

Explanation:

The correct answer is Option (4) → (A)-(IV), (B)-(III), (C)-(II), (D)-(I)

List-I (Matrix A)

List-II (Determinant of adj A)

(A) $\begin{bmatrix}2&1\\0&-1
\end{bmatrix}$

(IV) - 2

(B) $\begin{bmatrix}0&1\\4&-1
\end{bmatrix}$

(III) -4

(C) $\begin{bmatrix}1&2\\-3&-1
\end{bmatrix}$

(II) 5

(D) $\begin{bmatrix}4&-2\\3&0
\end{bmatrix}$

(I) 6

For a 2×2 matrix $A = \begin{bmatrix} a & b \\ c & d \end{bmatrix}$, $\det(\text{adj }A) = \det(A)$ because $\text{adj }A$ is 2×2 and $\det(\text{adj }A) = \det(A)^{n-1} = \det(A)^{2-1} = \det(A)$

Compute determinants:

(A) $A = \begin{bmatrix}2 & 1 \\ 0 & -1\end{bmatrix}$ → $\det(A) = 2 \cdot (-1) - 0 \cdot 1 = -2$ → $\det(\text{adj }A) = -2$ → (IV)

(B) $A = \begin{bmatrix}0 & 1 \\ 4 & -1\end{bmatrix}$ → $\det(A) = 0\cdot(-1) - 4\cdot1 = -4$ → $\det(\text{adj }A) = -4$ → (III)

(C) $A = \begin{bmatrix}1 & 2 \\ -3 & -1\end{bmatrix}$ → $\det(A) = 1\cdot(-1) - (-3\cdot2) = -1 + 6 = 5$ → $\det(\text{adj }A) = 5$ → (II)

(D) $A = \begin{bmatrix}4 & -2 \\ 3 & 0\end{bmatrix}$ → $\det(A) = 4\cdot0 - 3\cdot(-2) = 0 + 6 = 6$ → $\det(\text{adj }A) = 6$ → (I)