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Matrices · Question 14

JEE Main 2025 (Online) 4th April Evening ShiftMCQMedium📈 Topic in 35% papers+4−1
1

Let the matrix A = bmatrix 1 & 0 & 0 \ 1 & 0 & 1 \ 0 & 1 & 0 bmatrix satisfy An = An-2 + A2 - I for n 3. Then the sum of all the elements of A50 is :

  1. 44
  2. 39
  3. 52
  4. 53

Answer

(4) 53

Solution

An - An-2 = A2 - I for n 3

Putting n = 50, 48, , 4 (24 equations) and adding:

A50 - A2 = 24(A2 - I)

A50 = 25A2 - 24I

A2 = bmatrix 1 & 0 & 0 \ 1 & 0 & 1 \ 0 & 1 & 0 bmatrix bmatrix 1 & 0 & 0 \ 1 & 0 & 1 \ 0 & 1 & 0 bmatrix = bmatrix 1 & 0 & 0 \ 1 & 1 & 0 \ 1 & 0 & 1 bmatrix

Sum of elements of A2 = 5; sum of elements of I = 3

Sum of elements of A50 = 25 5 - 24 3 = 125 - 72 = 53

Answer: (4)

JEE Main 2025 (Online) 4th April Evening Shift

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2

Let A = bmatrix & -1 \ 6 & bmatrix, > 0, such that (A) = 0 and + = 1. If I denotes 2 2 identity matrix, then the matrix (I + A)8 is :

  1. bmatrix 257 & -64 \ 514 & -127 bmatrix
  2. bmatrix 766 & -255 \ 1530 & -509 bmatrix
  3. bmatrix 1025 & -511 \ 2024 & -1024 bmatrix
  4. bmatrix 4 & -1 \ 6 & -1 bmatrix
JEE Main 2025 (Online) 2nd April Morning Shift
3

Let A be a 3 3 real matrix such that A2(A - 2I) - 4(A - I) = O, where I and O are the identity and null matrices, respectively. If A5 = A2 + A + I, where , , and are real constants, then + + is equal to :

  1. 76
  2. 12
  3. 4
  4. 20
JEE Main 2025 (Online) 2nd April Evening Shift
4

Let S = \m Z : Am2 + Am = 3I - A-6 \, where A = bmatrix 2 & -1 \ 1 & 0 bmatrix. Then n(S) is equal to .

JEE Main 2025 (Online) 29th January Morning Shift
5

Let M denote the set of all real matrices of order 3 3 and let S = \-3, -2, -1, 1, 2\. Let S1 = \A = [aij] M : A = AT and aij S, i, j\, S2 = \A = [aij] M : A = -AT and aij S, i, j\, S3 = \A = [aij] M : a11 + a22 + a33 = 0 and aij S, i, j\. If n(S1 S2 S3) = 125 , then equals .

JEE Main 2025 (Online) 28th January Morning Shift
6

Let A = bmatrix 1 2 & -2 \ 0 & 1 bmatrix and P = bmatrix & - \ & bmatrix, > 0. If B = PAP , C = P B10P and the sum of the diagonal elements of C is mn, where (m, n) = 1, then m + n is :

  1. 127
  2. 2049
  3. 258
  4. 65
JEE Main 2025 (Online) 28th January Evening Shift

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