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Match List-I with List-II

List-I (Matrix A)List-II (Determinant of Adjoint of A)
(A) [3142]\begin{bmatrix} 3 & 1 \\ 4 & 2 \end{bmatrix}(I) 9
(B) [5−142]\begin{bmatrix} 5 & -1 \\ 4 & 2 \end{bmatrix}(II) 8
(C) [6−121]\begin{bmatrix} 6 & -1 \\ 2 & 1 \end{bmatrix}(III) 14
(D) [4133]\begin{bmatrix} 4 & 1 \\ 3 & 3 \end{bmatrix}(IV) 2

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

For a 2×2 matrix A, the relationship between the determinant of the adjoint and the determinant of the matrix is:

det(adj(A))=[det(A)]n−1\text{det(adj(A))} = [\text{det}(A)]^{n-1}

where n is the order of the matrix.

Since the matrices are 2×2, n = 2:

det(adj(A))=[det(A)]2−1\text{det(adj(A))} = [\text{det}(A)]^{2-1}

det(adj(A))=det(A)\text{det(adj(A))} = \text{det}(A)


For matrix [abcd]\begin{bmatrix} a & b \\ c & d \end{bmatrix}, the determinant is ad−bcad - bc.


For (A) [3142]\begin{bmatrix} 3 & 1 \\ 4 & 2 \end{bmatrix}:

det(A)=(3)(2)−(1)(4)\text{det}(A) = (3)(2) - (1)(4)

det(A)=6−4\text{det}(A) = 6 - 4

det(A)=2\text{det}(A) = 2

Matches with (IV)


For (B) [5−142]\begin{bmatrix} 5 & -1 \\ 4 & 2 \end{bmatrix}:

det(B)=(5)(2)−(−1)(4)\text{det}(B) = (5)(2) - (-1)(4)

det(B)=10+4\text{det}(B) = 10 + 4

det(B)=14\text{det}(B) = 14

Matches with (III)


For (C) [6−121]\begin{bmatrix} 6 & -1 \\ 2 & 1 \end{bmatrix}:

det(C)=(6)(1)−(−1)(2)\text{det}(C) = (6)(1) - (-1)(2)

det(C)=6+2\text{det}(C) = 6 + 2

det(C)=8\text{det}(C) = 8

Matches with (II)


For (D) [4133]\begin{bmatrix} 4 & 1 \\ 3 & 3 \end{bmatrix}:

det(D)=(4)(3)−(1)(3)\text{det}(D) = (4)(3) - (1)(3)

det(D)=12−3\text{det}(D) = 12 - 3

det(D)=9\text{det}(D) = 9

Matches with (I)


The correct matching is:

(A) → (IV)

(B) → (III)

(C) → (II)

(D) → (I)

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