Let $P=\left[a_{i j}\right]$ be a $3 \times 3$ matrix and let $Q=\left[b_{i j}\right]$ where $b_{i j}=2^{i+j} a_{i j} ~\forall ~1 ≤ i, j ≥ 3$. If the determinant of P is 2, then the determinant of Q is: |
$2^{13}$ $2^{12}$ $2^{11}$ $2^{10}$ |
$2^{13}$ |
The correct answer is Option (1) → $2^{13}$ $|P|=\begin{vmatrix}a_{11}&a_{12}&a_{13}\\a_{21}&a_{22}&a_{23}\\a_{31}&a_{32}&a_{33}\end{vmatrix}=2$ $Q=\begin{vmatrix}2^2a_{11}&2^3a_{12}&2^4a_{13}\\2^3a_{21}&2^4a_{22}&2^5a_{23}\\2^4a_{31}&2^5a_{32}&2^6a_{33}\end{vmatrix}=2$ $⇒Q=DPD$ [D → Diagonal Matrix] $D=\begin{bmatrix} 2^1 & 0 & 0 \\ 0 & 2^2 & 0 \\ 0 & 0 & 2^3 \end{bmatrix}⇒|D|=2^1.2^2.2^3=2^6$ $∴|Q|=|DPD|$ $=|D|^2|P|$ $=(2^6)^2(2)=2^{13}$ |