Mathematics · Matrices

JEE Main 2025 — 3 April, Morning Shift — Question 20

Let A be a matrix of order 3×33 \times 3 and ∣A∣=5|\mathrm{A}|=5. If ∣2adj⁡(3 Aadj⁡(2 A))∣=2α.3β.5γα,β,γ∈N|2 \operatorname{adj}(3 \mathrm{~A} \operatorname{adj}(2 \mathrm{~A}))|=2^{\alpha} .3^{\beta} .5^{\gamma} \alpha, \beta, \gamma \in \mathrm{N} then

α+β+γ\alpha+\beta+\gamma is equal to

  1. Option A:

    25

  2. Option B:

    26

  3. Option C:

    27

    Correct
  4. Option D:

    28

Answer: C

Step-by-step solution

∣2\mid 2 adj (3 Aadj⁡(2 A))∣(3 \mathrm{~A} \operatorname{adj}(2 \mathrm{~A})) \mid

23.∣3 Aadj⁡(2 A)∣22^{3} .|3 \mathrm{~A} \operatorname{adj}(2 \mathrm{~A})|^{2}

23⋅(33)2⋅∣ A∣2⋅∣adj⁡(2 A)∣22^{3} \cdot\left(3^{3}\right)^{2} \cdot|\mathrm{~A}|^{2} \cdot|\operatorname{adj}(2 \mathrm{~A})|^{2}

23⋅36⋅∣ A∣2⋅(∣2 A∣2)22^{3} \cdot 3^{6} \cdot|\mathrm{~A}|^{2} \cdot\left(|2 \mathrm{~A}|^{2}\right)^{2}

23⋅36⋅∣ A∣2[(23)2⋅∣ A∣2]22^{3} \cdot 3^{6} \cdot|\mathrm{~A}|^{2}\left[\left(2^{3}\right)^{2} \cdot|\mathrm{~A}|^{2}\right]^{2}

23⋅36⋅∣ A∣2⋅212⋅∣ A∣42^{3} \cdot 3^{6} \cdot|\mathrm{~A}|^{2} \cdot 2^{12} \cdot|\mathrm{~A}|^{4}

215.36.∣A∣62^{15} .3^{6} .|\mathrm{A}|^{6}

215⋅36⋅56=2α⋅3β⋅5γ2^{15} \cdot 3^{6} \cdot 5^{6}=2^{\alpha} \cdot 3^{\beta} \cdot 5^{\gamma}

α=15,β=6,γ=6\alpha=15, \quad \beta=6, \quad \gamma=6

α+β+γ=27\alpha+\beta+\gamma=27

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Subject
Mathematics
Chapter
Matrices
Topic
Adjoint of a Square Matrix
Let A be a matrix of order 3 × 3 and A =5 . If 2 adj (3 A adj (2 A ))… | JEE Main 2025 PYQ with Solution · DhiX AI