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JEE Main 202310 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
10 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Matrices

JEE Main 2023 · 10 April · Morning Shift · Mathematics · Matrices

If A is a 3 × 3 matrix and |A| = 2 , then |3 adj (|3A| A ^ 2 )| is...

If AA is a 3×33 \times 3 matrix and ∣A∣=2\left|A\right| = 2, then \left|3 adj \left(\left|3A\right|{A}^{2}\right)\right| is equal to

Options

  1. A312⋅611{3}^{12} \cdot {6}^{11}
  2. B312⋅610{3}^{12} \cdot {6}^{10}
  3. C310⋅611{3}^{10} \cdot {6}^{11}
  4. D311⋅610{3}^{11} \cdot {6}^{10}

Correct answer

D. 311⋅610{3}^{11} \cdot {6}^{10}

Step-by-step solution

We need to find the value of ∣3adj(∣3A∣A2)∣\left|3adj\left(\left|3A\right|{A}^{2}\right)\right|

We know that \left|kA\right| = {k}^{n}\left|A\right|wherewherenistheorderofthematrixandis the order of the matrix andkisaconstant.</p><p>is a constant.</p><p>⇒ \left|3A\right| = {3}^{3}\left(2\right)</p><p></p><p>⇒ \left|3adj\left(\left|3A\right|{A}^{2}\right)\right| = {3}^{3}\left|adj\left(\left({3}^{3} \cdot 2\right){A}^{2}\right)\right|</p><p>Weknowthat</p><p>We know thatadj\left(kA\right) = {k}^{n - 1}adj\left(A\right)</p><p></p><p>= {3}^{3}\left|{\left({3}^{3} \cdot 2\right)}^{2}adj\left({A}^{2}\right)\right|</p><p>Nowweknowthat∣adjA∣=∣A∣n−1</p><p>Now we know that \left|adjA\right| = {\left|A\right|}^{n - 1}

=33((33⋅2)2)3∣adj(A2)∣= {3}^{3}{\left({\left({3}^{3} \cdot 2\right)}^{2}\right)}^{3}\left|adj\left({A}^{2}\right)\right|

=33(33⋅2)6∣A2∣3−1= {3}^{3}{\left({3}^{3} \cdot 2\right)}^{6}{\left|{A}^{2}\right|}^{3 - 1}

=33(33⋅2)6(2)4= {3}^{3}{\left({3}^{3} \cdot 2\right)}^{6}{\left(2\right)}^{4}

=210⋅321= {2}^{10} \cdot {3}^{21}

Hence, the required answer is 210⋅321{2}^{10} \cdot {3}^{21}=610⋅311= {6}^{10} \cdot {3}^{11}

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