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Matrices · Question 6

JEE Main 2026 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 6% papers+4−1
1

Let A, B and C be three 2 × 2 matrices with real entries such that B = (I + A)-1 and A + C = I. If BC = bmatrix 1 & -5 \ -1 & 2 bmatrix and CB bmatrix x1 \ x2 bmatrix = bmatrix 12 \ -6 bmatrix, then x1 + x2 is

  1. 4
  2. 2
  3. 0
  4. −2

Answer

(3) 0

Solution

C = I − A, B = (I + A)-1

(I - A)(I + A) = I - A2 = (I + A)(I - A)

Pre- and post-multiplying by (I + A)-1:

(I + A)-1(I - A) = (I - A)(I + A)-1

BC = CB

bmatrix 1 & -5 \ -1 & 2 bmatrix bmatrix x1 \ x2 bmatrix = bmatrix 12 \ -6 bmatrix

x1 - 5x2 = 12 and -x1 + 2x2 = -6

Adding: -3x2 = 6 x2 = -2, x1 = 2

x1 + x2 = 0

Answer: (3)

JEE Main 2026 (Online) 28th January Morning Shift

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2

Let A = bmatrix 3 & -4 \ 1 & -1 bmatrix and B be two matrices such that A100 = 100B + I. Then the sum of all the elements of B100 is

JEE Main 2026 (Online) 28th January Evening Shift
3

The number of 3 2 matrices A, which can be formed using the elements of the set \-2, -1, 0, 1, 2\ such that the sum of all the diagonal elements of ATA is 5, is

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4

Let A = bmatrix 0 & 2 & -3 \ -2 & 0 & 1 \ 3 & -1 & 0 bmatrix and B be a matrix such that B(I - A) = I + A. Then the sum of the diagonal elements of BTB is equal to

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5

If A = bmatrix 2 & 3 \ 3 & 5 bmatrix, then the determinant of the matrix (A2025 - 3 A2024 + A2023 ) is

  1. 12
  2. 24
  3. 28
  4. 16
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6

For some , R, let A = bmatrix & 2 \ 1 & 2 bmatrix and B = bmatrix 1 & 1 \ 1 & bmatrix be such that A2 - 4A + 2I = B2 - 3B + I = O. Then ( ( adj(A3 - B3)))2 is equal to .

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7

For the matrices A = bmatrix 3 & -4 \ 1 & -1 bmatrix and B = bmatrix -29 & 49 \ -13 & 18 bmatrix, if (A15 + B) bmatrix x \ y bmatrix = bmatrix 0 \ 0 bmatrix, then among the following which one is true?

  1. x = 16, y = 3
  2. x = 5, y = 7
  3. x = 11, y = 2
  4. x = 18, y = 11
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8

Let A = bmatrix & 0 & - \ 0 & 1 & 0 \ & 0 & bmatrix. If for some (0, ), A2 = AT, then the sum of the diagonal elements of the matrix (A + I)3 + (A - I)3 - 6A is equal to .

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9

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
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10

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  1. bmatrix 257 & -64 \ 514 & -127 bmatrix
  2. bmatrix 766 & -255 \ 1530 & -509 bmatrix
  3. bmatrix 1025 & -511 \ 2024 & -1024 bmatrix
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11

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
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