Question 43

Mathematics Determinants Hard

Which of the following statements are TRUE?

(A) If each element in a row is a constant multiplier of corresponding element of another row of a determinant, then the value of the determinant is always non-zero.
(B) If each element on one side of the principal diagonal of a determinant is zero, then the value of the determinant is the product of the diagonal elements.
(C) The value of determinant of skew symmetric matrix of odd order is always non-zero.
(D) If A is non-singular matrix of order three, then \( |\operatorname{adj} \mathrm{A}|=|\mathrm{A}|^{2} \)
Choose the correct answer from the options given below:

(A) (B) and (D) only
(B) (A) and(B) only
(C) (A), (B) and (C) only
(D) (A), (C) and (D) only
✓ Correct Answer: Option A Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

Statement (A) "If each element in a row is a constant multiplier of the corresponding element of another row of a determinant, then the value of the determinant is always non-zero." - This statement is false because if any row (or column) of a determinant is a constant multiple of another row (or column), the determinant is zero. - Mathematically, if two rows (or columns) are linearly dependent, then: \[ |A| = 0 \] Statement (B) "If each element on one side of the principal diagonal of a determinant is zero, then the value of the determinant is the product of the diagonal elements." - This describes a triangular matrix (upper or lower triangular matrix). - The determinant of a triangular matrix is given by: \[ |A| = \prod_{i=1}^{n} a_{ii} \] where \( a_{ii} \) are the diagonal elements. - Since the given condition matches this form, this statement is true. Statement (C) *"The value of determinant of a skew-symmetric matrix of odd order is always non-zero."* - A skew-symmetric matrix satisfies the property: \[ A^T = -A \] - If the order \( n \) of a skew-symmetric matrix is odd, then its determinant is always zero, i.e., \[ \det(A) = 0 \] - Since the statement claims it is non-zero, it is false. Statement (D) *"If \( A \) is a non-singular matrix of order three, then \( |\text{adj} A| = |A|^2 \)."* - For any non-singular square matrix \( A \) of order \( n \), the determinant of the adjugate is given by: \[ |\text{adj}(A)| = |A|^{n-1} \] - For a 3×3 matrix: \[ |\text{adj}(A)| = |A|^{3-1} = |A|^2 \] - Since the given statement correctly follows this property, it is true. Final Answer: - The correct statements are (B) and (D). - Thus, the correct answer is: \[ \boxed{\text{(B) and (D) only}} \]

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