Matrices & Determinants
Matrices and Determinants
Grade Class 12
Question:
For any 3 × 3 matrix M, let |M| denote the determinant of M. Let <br>E = <math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced open="["><mtable><mtr><mtd><mn>1</mn></mtd><mtd><mn>2</mn></mtd><mtd><mn>3</mn></mtd></mtr><mtr><mtd><mn>2</mn></mtd><mtd><mn>3</mn></mtd><mtd><mn>4</mn></mtd></mtr><mtr><mtd><mn>8</mn></mtd><mtd><mn>13</mn></mtd><mtd><mn>18</mn></mtd></mtr></mtable></mfenced></math>, P = <math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced open="["><mtable><mtr><mtd><mn>1</mn></mtd><mtd><mn>0</mn></mtd><mtd><mn>0</mn></mtd></mtr><mtr><mtd><mn>0</mn></mtd><mtd><mn>0</mn></mtd><mtd><mn>1</mn></mtd></mtr><mtr><mtd><mn>0</mn></mtd><mtd><mn>1</mn></mtd><mtd><mn>0</mn></mtd></mtr></mtable></mfenced></math> and F = <math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced open="["><mtable><mtr><mtd><mn>1</mn></mtd><mtd><mn>3</mn></mtd><mtd><mn>2</mn></mtd></mtr><mtr><mtd><mn>1</mn></mtd><mtd><mn>3</mn></mtd><mtd><mn>2</mn></mtd></mtr><mtr><mtd><mn>2</mn></mtd><mtd><mn>4</mn></mtd><mtd><mn>3</mn></mtd></mtr></mtable></mfenced></math>.<br>If Q is a nonsingular matrix of order 3 × 3, then which of the following statements is (are) TRUE?
(A) F = PEP and P<sup>2</sup> = I
(B) |EQ + PFQ<sup>-1</sup>| = |EQ| + |PFQ<sup>-1</sup>|
(C) |(EF)<sup>3</sup>| > |EF|<sup>2</sup>
(D) Sum of the diagonal entries of P<sup>-1</sup> EP + F is equal to the sum of diagonal entries of E + P<sup>-1</sup> FP
Step-by-Step Solution
Key Concept: Properties of determinants, matrix multiplication, and trace of matrices.
The matrix P is an elementary permutation matrix. Calculating P^2 gives the identity matrix I. Checking the relation F = PEP involves matrix multiplication. The determinant property |A+B| = |A|+|B| is generally false. The trace property Tr(A+B) = Tr(A) + Tr(B) and Tr(P^-1 EP) = Tr(E) are used to verify option (D).
Correct Answer: A,B,D