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Determinants

JEE Main 2024 (Online) 4th April Morning ShiftMCQMedium📈 Topic in 38% papers+4−1
Ques. 1JEE Main 2024, 4 April (Morning Shift)

Let (0, ) and A= bmatrix1 & 2 & \ 1 & 0 & 1 \ 0 & 1 & 2 bmatrix. If det ( adj (2A-AT ) adj (A-2AT ) )=28, then ( det(A))2 is equal to:

  1. 16
  2. 36
  3. 49
  4. 1

Answer

(1) 16

Solution

Let P=A-2AT, Q=2A-AT QT=2AT-A=-P

|Q|=|-P|=(-1)3|P|=-|P|

| adjM|=|M|2 for order 3: |Q|2|P|2=28 |P|4=28 |P|= 4

P= bmatrix1&2& \\1&0&1\\0&1&2 bmatrix- bmatrix2&2&0\\4&0&2\\2 &2&4 bmatrix= bmatrix-1&0& \\-3&0&-1\\-2 &-1&-2 bmatrix

Expanding along C2: |P|=-(-1)(1+3 )=1+3

1+3 = 4 =1 ( >0)

|A|=1(0-1)-2(2-0)+1(1-0)=-4 ( detA)2=16

Answer: (1)

Keep practising — Determinants

Ques. 2JEE Main 2024, 4 April (Morning Shift)

If the system of equations x+( 2 )y+( 2 )z=0 x+( )y+( )z=0 x+( )y-( )z=0 has a non-trivial solution, then (0, 2 ) is equal to :

  1. 5 24
  2. 11 24
  3. 7 24
  4. 3 4
Ques. 3JEE Main 2024, 4 April (Morning Shift)

Let A be a 3 3 matrix of non-negative real elements such that A bmatrix1\\1\\1 bmatrix=3 bmatrix1\\1\\1 bmatrix. Then the maximum value of (A) is .

Ques. 4JEE Main 2024, 1 February (Morning Shift)

If A= bmatrix 2 & 1\ -1 & 2 bmatrix, B= bmatrix1 & 0\ 1 & 1 bmatrix, C=ABAT and X=ATC2A, then is equal to :

  1. 243
  2. 729
  3. 27
  4. 891
Ques. 5JEE Main 2024, 1 February (Morning Shift)

If the system of equations 2x+3y-z=5 x+ y+3z=-4 3x-y+ z=7 has infinitely many solutions, then 13 is equal to :

  1. 1110
  2. 1120
  3. 1210
  4. 1220
Ques. 6JEE Main 2024, 1 February (Evening Shift)

Let the system of equations x+2 y+3 z=5, 2 x+3 y+z=9, 4 x+3 y+ z= have infinite number of solutions. Then +2 is equal to :

  1. 22
  2. 17
  3. 15
  4. 28
Ques. 7JEE Main 2024, 31 January (Morning Shift)

If the system of linear equations x-2y+z=-4 2x+ y+3z=5 3x-y+ z=3 has infinitely many solutions, then 12 +13 is equal to

  1. 60
  2. 54
  3. 64
  4. 58
Ques. 8JEE Main 2024, 31 January (Morning Shift)

If f(x)= vmatrix x3 & 2x2+1 & 1+3x \ 3x2+2 & 2x & x3+6 \ x3-x & 4 & x2-2 vmatrix for all x R, then 2f(0)+f'(0) is equal to

  1. 24
  2. 18
  3. 42
  4. 48
Ques. 9JEE Main 2024, 31 January (Evening Shift)

Let A be a 3 3 real matrix such that A pmatrix1\\0\\1 pmatrix=2 pmatrix1\\0\\1 pmatrix, A pmatrix-1\\0\\1 pmatrix=4 pmatrix-1\\0\\1 pmatrix, A pmatrix0\\1\\0 pmatrix=2 pmatrix0\\1\\0 pmatrix. Then, the system (A-3I) pmatrixx\ \ pmatrix= pmatrix1\\2\\3 pmatrix has :

  1. exactly two solutions
  2. infinitely many solutions
  3. unique solution
  4. no solution
Ques. 10JEE Main 2024, 31 January (Evening Shift)

Let A be a 3 3 matrix and (A)=2. If n= ( 2024 times adj(adj( (adj A)))), then the remainder when n is divided by 9 is equal to .

Ques. 11JEE Main 2024, 30 January (Morning Shift)

If f(x)= vmatrix2 4x & 2 4x & 3+ 2 2x\ 3+2 4x & 2 4x & 2 2x\ 2 4x & 3+2 4x & 2 2x vmatrix, then 15f'(0) is equal to :

  1. 2
  2. 1
  3. 0
  4. 6

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