Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 202313 AprilEvening Shift
Exam
JEE Main
Year
2023
Date
13 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Matrices

JEE Main 2023 · 13 April · Evening Shift · Mathematics · Matrices

Let for A = [ cases 1 & 2 & 3 α & 3 & 1 1 & 1 & 2 cases ], |A| = 2...

Let for A = \left[\begin{cases}1 & 2 & 3 \\ \alpha & 3 & 1 \\ 1 & 1 & 2\end{cases}\right], \left|A\right| = 2. If ∣2adj(2adj(2A))∣=32n| 2 adj ( 2 adj ( 2A ) ) | = {32}^{n}, then 3n+α3n + \alpha is equal to

Options

  1. A99
  2. B1111
  3. C1212
  4. D1010

Correct answer

B. 1111

Step-by-step solution

Given that A = \left[\begin{cases}1 & 2 & 3 \\ \alpha & 3 & 1 \\ 1 & 1 & 2\end{cases}\right]

⇒∣A∣=2⇒ | A | = 2

⇒1(6−1)−α−7=2⇒ 1\left(6 - 1\right) - \alpha - 7 = 2

⇒−α−2=2⇒ - \alpha - 2 = 2

⇒α=−4⇒ \alpha = - 4

⇒∣2adj(2adj(2A))∣=32n⇒ | 2 adj ( 2 adj ( 2A ) ) | = {32}^{n}

We know that \left|kA\right| = {k}^{n}∣A∣\left|A\right|, adj(adj(A))=∣A∣(n−1)2adj ( adj ( A ) ) = {\left|A\right|}^{{\left(n - 1\right)}^{2}} and adj(kA)=kn−1adj(A)adj\left(kA\right) = {k}^{n - 1}adj\left(A\right).

=23∣adj(2adj(2A))∣= {2}^{3} | adj ( 2 adj ( 2A ) ) |

=23∣23−1adj(adj(2A))∣= {2}^{3} | {2}^{3 - 1} adj ( adj ( 2A ) ) |

=23⋅(4)3∣adj(adj(2A))∣= {2}^{3} \cdot ( 4{)}^{3} | adj ( adj ( 2A ) ) |

=29∣2A∣(2)2= {2}^{9} | 2A{|}^{( 2{)}^{2}}

=29⋅∣2A∣4= {2}^{9} \cdot | 2A{|}^{4}

=29⋅212∣A∣4= {2}^{9} \cdot {2}^{12} | A{|}^{4}

=221⋅24=225=(32)n=(2)5n= {2}^{21} \cdot {2}^{4} = {2}^{25} = ( 32{)}^{n} = ( 2{)}^{5n}

∴n=5∴ n = 5

⇒3n+α=15−4=11⇒ 3n + \alpha = 15 - 4 = 11

Hence this is the correct option.

Practice Matrices on Quantrex Academy →

More from Matrices

Which one of the following matrices can be obtained by performing elementary row… JEE Advanced 2026Consider the matrix M = bmatrix 2 & -1 1 & 0 bmatrix . Let p, q, r, s, a, b, c and d be… JEE Advanced 2026For real numbers α, β, γ, δ and μ , consider the matrix M = bmatrix α & 1 2 & - 1 2 1 3 &… JEE Advanced 2026Let ℝ denote the set of all real numbers and let i = -1 . Consider the matrices S =… JEE Advanced 2026Let A = bmatrix α & 1 & 2 2 & 3 & 0 0 & 4 & 5 bmatrix and B = bmatrix 1 & 0 & 0 0 & -5α &… JEE Main 2026Let A = bmatrix 1 & 0 & 0 3 & 1 & 0 9 & 3 & 1 bmatrix and B = [b_ ij ] , 1 ≤ i, j ≤ 3 .… JEE Main 2026Let A = bmatrix -1 & 1 & -1 1 & 0 & 1 0 & 0 & 1 bmatrix satisfy A^2 + α(adj(adj(A))) +… JEE Main 2026Let M be a 3 × 3 matrix such that M pmatrix 1 0 0 pmatrix = pmatrix 1 2 3 pmatrix , M… JEE Main 2026Let A be a 3 × 3 matrix such that A^T bmatrix 1 0 1 bmatrix = bmatrix 5 2 2 bmatrix , A^T… JEE Main 2026Let A= bmatrix 1 & 2 & 7 4 & -2 & 8 3 & 8 & -7 bmatrix and (A-α I)=0 , where α is a real… JEE Main 2026Let S = \ A = bmatrix a & b c & d bmatrix : a, b, c, d ∈ \ 0, 1, 2, 3, 4\ and A^2 - 4A +… JEE Main 2026Let A = bmatrix 1 & 1 & 2 -2 & 0 & 1 1 & 3 & 5 bmatrix . Then the sum of all elements of… JEE Main 2026Consider the matrices A = bmatrix 2 & -2 4 & -2 bmatrix and B = bmatrix 3 & 9 1 & 3… JEE Main 2026Let A = bmatrix 1 & 2 1 & α bmatrix and B = bmatrix 3 & 3 β & 2 bmatrix . If A^2 - 4A + I… JEE Main 2026Let A=[ array ll 3 & -4 1 & -1 array ] and B be two matrices such that A^ 100 =100 B+I .… JEE Main 2026Let A, B and C be three 2 × 2 matrices with real entries such that B=(I+A)^ -1 and A+C=I… JEE Main 2026 Full Matrices list Matrices JEE Maths PYQsJEE Mathematics PYQs All JEE Main PYQs