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Determinants

JEE Main 2024 (Online) 31st January Morning ShiftMCQMedium📈 Topic in 59% papers+4−1
Ques. 1JEE 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

Answer

(4) 58

Solution

For infinitely many solutions, D = D1 = D2 = D3 = 0 (Cramer's rule).

D2 = vmatrix 1 & -4 & 1 \ 2 & 5 & 3 \ 3 & 3 & vmatrix = (5 - 9) + 4(2 - 9) + (6 - 15) = 13 - 54

D2 = 0 gives = 5413.

D = vmatrix 1 & -2 & 1 \ 2 & & 3 \ 3 & -1 & vmatrix = ( + 3) + 2(2 - 9) + (-2 - 3 ) = - 3 + 4 - 17

Putting = 5413 in D = 0: ( 5413 - 3 ) = 17 - 21613, i.e. 15 13 = 513, so = 13

With these values D1 = D3 = 0 as well, so the system indeed has infinitely many solutions.

12 + 13 = 4 + 54 = 58

Answer: (4)

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Ques. 2JEE 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. 3JEE 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. 4JEE 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. 5JEE 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
Ques. 6JEE Main 2024, 30 January (Morning Shift)

Consider the system of linear equations x+y+z=4 , x+2y+2 z=10 , x+3y+4 2z= 2+15 where , . Which one of the following statements is NOT correct ?

  1. The system has unique solution if 12 and 1, 15
  2. The system has infinite number of solutions if = 12 and =15
  3. The system is consistent if 12
  4. The system is inconsistent if = 12 and 1
Ques. 7JEE Main 2024, 30 January (Evening Shift)

Let R= pmatrixx&0&0\\0&y&0\\0&0&z pmatrix be a non-zero 3 3 matrix, where x =y ( + 2 3 )=z ( + 4 3 ) 0, (0,2 ). For a square matrix M, let trace (M) denote the sum of all the diagonal entries of M. Then, among the statements: (I) Trace (R)=0 (II) If trace (adj(adj(R)))=0, then R has exactly one non-zero entry.

  1. Only (I) is true
  2. Only (II) is true
  3. Both (I) and (II) are true
  4. Neither (I) nor (II) is true
Ques. 8JEE Main 2024, 30 January (Evening Shift)

Consider the system of linear equations x+y+z=5, x+2y+ 2 z=9, x+3y+ z= , where , R. Then, which of the following statements is NOT correct?

  1. System is consistent if 1 and =13
  2. System is inconsistent if =1 and 13
  3. System has unique solution if 1 and 13
  4. System has infinite number of solutions if =1 and =13
Ques. 9JEE Main 2024, 29 January (Morning Shift)

Let A= bmatrix1&0&0\\0& & \\0& & bmatrix and |2A|3=221 where , Z. Then a value of is

  1. 9
  2. 17
  3. 3
  4. 5
Ques. 10JEE Main 2024, 29 January (Evening Shift)

Let A= bmatrix2&1&2\\6&2&11\\3&3&2 bmatrix and P= bmatrix1&2&0\\5&0&2\\7&1&5 bmatrix. The sum of the prime factors of |P-1AP-2I | is equal to

  1. 66
  2. 27
  3. 23
  4. 26
Ques. 11JEE Main 2024, 29 January (Evening Shift)

Let for any three distinct consecutive terms a, b, c of an A.P, the lines ax+by+c=0 be concurrent at the point P and Q( , ) be a point such that the system of equations x+y+z=6, 2x+5y+ z= and x+2y+3z=4, has infinitely many solutions. Then (PQ)2 is equal to .

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