Skip to main contentSkip to solution

If A=[5243]A = \begin{bmatrix} 5 & 2 \\ 4 & 3 \end{bmatrix} is a given matrix, then which of the following statements are correct?

(A) ∣A∣=7|A| = 7

(B) minor of 3=−53 = -5

(C) co-factor of 2=−42 = -4

(D) adj(A)=[3−2−45]adj(A) = \begin{bmatrix} 3 & -2 \\ -4 & 5 \end{bmatrix}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

Given matrix A=[5243]A = \begin{bmatrix} 5 & 2 \\ 4 & 3 \end{bmatrix}


Checking Statement (A): ∣A∣=7|A| = 7

For a 2×2 matrix [abcd]\begin{bmatrix} a & b \\ c & d \end{bmatrix}, the determinant is ad−bcad - bc

∣A∣=(5)(3)−(2)(4)|A| = (5)(3) - (2)(4)

∣A∣=15−8|A| = 15 - 8

∣A∣=7|A| = 7

Statement (A) is correct.


Checking Statement (B): minor of 3=−53 = -5

Element 3 is in row 2, column 2.

Deleting row 2 and column 2 leaves only element 5.

Minor of 3=53 = 5

Statement (B) is incorrect.


Checking Statement (C): co-factor of 2=−42 = -4

Element 2 is in row 1, column 2 (so i=1i=1, j=2j=2).

Deleting row 1 and column 2 leaves only element 4.

Minor of 2=42 = 4

Cofactor =(−1)i+j×minor= (-1)^{i+j} \times \text{minor}

Cofactor =(−1)1+2×4= (-1)^{1+2} \times 4

Cofactor =(−1)3×4= (-1)^3 \times 4

Cofactor =−4= -4

Statement (C) is correct.


Checking Statement (D): adj(A)=[3−2−45]adj(A) = \begin{bmatrix} 3 & -2 \\ -4 & 5 \end{bmatrix}

For a 2×2 matrix [abcd]\begin{bmatrix} a & b \\ c & d \end{bmatrix}, the adjoint is [d−b−ca]\begin{bmatrix} d & -b \\ -c & a \end{bmatrix}

adj(A)=[3−2−45]adj(A) = \begin{bmatrix} 3 & -2 \\ -4 & 5 \end{bmatrix}

Statement (D) is correct.


Statements (A), (C), and (D) are correct.

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question