ExamBro
ExamBro
JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant

Let \(A=\left\{a_{i}\right\}\) be a \(3 \times 3\) matrix, where \(a_{i j}=\left\{\begin{aligned}(-1)^{j-i} & \text { if } i < j \\ 2 & \text { if } i=j \\(-1)^{i+j} & \text { if } i > j \end{aligned}\right.\)  then \(\operatorname{det}\left(3 \operatorname{Adj}\left(2 \mathrm{~A}^{-1}\right)\right)\) is equal to \(.....\)

  1. A \(126\)
  2. B \(12\)
  3. C \(144\)
  4. D \(108\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(108\)

Step-by-step Solution

Detailed explanation

\(A=\left[\begin{array}{ccc}2 & -1 & 1 \\ -1 & 2 & -1 \\ 1 & -1 & 2\end{array}\right]\) \(|\mathrm{A}|=4\) \(\left|3 \operatorname{adj}\left(2 \mathrm{~A}^{-1}\right)\right|=\left|3 \cdot 2^{2} \operatorname{adj}\left(\mathrm{A}^{-1}\right)\right|\)…
From JEE Mains
Explore more questions on app