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Determinant of Scaled Matrix Entries with Power Factors

Let P=[aij]P = [a_{ij}] denote a 3×33 \times 3 matrix and Q=[bij]Q = [b_{ij}] be defined such that bij=2i+jaijb_{ij} = 2^{i+j} a_{ij} for all 1≤i,j≤31 \le i, j \le 3. If det⁡(P)=2\det(P) = 2, then the determinant of matrix QQ is equal to

Options

A

2102^{10}

B

2112^{11}

C

2122^{12}

D

2132^{13}

Correct

Step-by-Step Solution

To find the determinant of matrix QQ, we write the matrices PP and QQ explicitly:

P=[a11a12a13a21a22a23a31a32a33]P = \begin{bmatrix} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33} \end{bmatrix}

The entries of matrix Q=[bij]Q = [b_{ij}] are given by bij=2i+jaij=2i⋅2j⋅aijb_{ij} = 2^{i+j} a_{ij} = 2^i \cdot 2^j \cdot a_{ij} for 1≤i,j≤31 \le i, j \le 3. Thus, the matrix QQ is:

Q=[21+1a1121+2a1221+3a1322+1a2122+2a2222+3a2323+1a3123+2a3223+3a33]Q = \begin{bmatrix} 2^{1+1} a_{11} & 2^{1+2} a_{12} & 2^{1+3} a_{13} \\ 2^{2+1} a_{21} & 2^{2+2} a_{22} & 2^{2+3} a_{23} \\ 2^{3+1} a_{31} & 2^{3+2} a_{32} & 2^{3+3} a_{33} \end{bmatrix}

Using the properties of determinants:

  1. We can factor out 212^1 from the first row (R1R_1), 222^2 from the second row (R2R_2), and 232^3 from the third row (R3R_3):
det⁡(Q)=21⋅22⋅23∣21a1122a1223a1321a2122a2223a2321a3122a3223a33∣\det(Q) = 2^1 \cdot 2^2 \cdot 2^3 \begin{vmatrix} 2^1 a_{11} & 2^2 a_{12} & 2^3 a_{13} \\ 2^1 a_{21} & 2^2 a_{22} & 2^3 a_{23} \\ 2^1 a_{31} & 2^2 a_{32} & 2^3 a_{33} \end{vmatrix}
  1. Next, from the resulting determinant, we can factor out 212^1 from the first column (C1C_1), 222^2 from the second column (C2C_2), and 232^3 from the third column (C3C_3):
det⁡(Q)=(21⋅22⋅23)(21⋅22⋅23)∣a11a12a13a21a22a23a31a32a33∣\det(Q) = (2^1 \cdot 2^2 \cdot 2^3)(2^1 \cdot 2^2 \cdot 2^3) \begin{vmatrix} a_{11} & a_{12} & a_{13} \\ a_{21} & a_{22} & a_{23} \\ a_{31} & a_{32} & a_{33} \end{vmatrix}

Combining the powers of 22:

det⁡(Q)=21+2+3⋅21+2+3⋅det⁡(P)=26⋅26⋅det⁡(P)=212det⁡(P)\det(Q) = 2^{1+2+3} \cdot 2^{1+2+3} \cdot \det(P) = 2^6 \cdot 2^6 \cdot \det(P) = 2^{12} \det(P)

Given that det⁡(P)=2\det(P) = 2, we obtain:

det⁡(Q)=212⋅2=213\det(Q) = 2^{12} \cdot 2 = 2^{13}

Hence, the correct option is (D).