Matrices & Determinants
Determinant Calculations
Grade 12
Question:
<p><strong>Column I (A):</strong> If A is a square matrix of order 3 and \(\det(A) = 3\), then \(\det(6A^{-1})\) is divisible by</p><p><strong>Column II:</strong> Match with the appropriate divisor from options (p), (q), (r), (s)</p>
Step-by-Step Solution
Key Concept: For a scalar multiple of a matrix: $\det(kA) = k^n\det(A)$ where n is the order. Also, $\det(A^{-1}) = 1/\det(A)$.
<p><strong>For statement A:</strong> If A is a square matrix of order 3 and $\det(A) = 3$, find $\det(6A^{-1})$.</p><p>$\det(6A^{-1}) = \det(6I \cdot A^{-1}) = 6^3 \cdot \det(A^{-1})$</p><p>Since $\det(A^{-1}) = \frac{1}{\det(A)} = \frac{1}{3}$</p><p>$\det(6A^{-1}) = 216 \cdot \frac{1}{3} = 72$</p><p>72 is divisible by 3.</p><p><strong>A matches with (p) 3</strong></p>
Correct Answer: A→p