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Relations and Functions (Class 12)

JEE Main 2025 (Online) 2nd April Morning ShiftMCQMedium📈 Topic in 22% papers+4−1
Ques. 1JEE Main 2025, 2 April (Morning Shift)

Let f : R R be a twice differentiable function such that ( x y)(f(2x + 2y) - f(2x - 2y)) = ( x y)(f(2x + 2y) + f(2x - 2y)), for all x, y R. If f'(0) = 12, then the value of 24f'' ( 5 3 ) is :

  1. 2
  2. 3
  3. -3
  4. -2

Answer

(3) -3

Solution

Collecting the f(2x + 2y) and f(2x - 2y) terms gives

f(2x + 2y)( x y - x y) = f(2x - 2y)( x y + x y)

f(2x + 2y) (x - y) = f(2x - 2y) (x + y)

f(2(x + y)) (x + y) = f(2(x - y)) (x - y) for all x, y

Since this holds for all x, y, f(2t) t = k (constant), so f(x) = k x2.

Then f'(x) = k2 x2, and f'(0) = k2 = 12 gives k = 1.

Hence f(x) = x2 and f''(x) = - 14 x2.

24f'' ( 5 3 ) = 24 (- 14 ) 5 6 = -6 12 = -3

Answer: (3)

Keep practising — Relations and Functions (Class 12)

Ques. 2JEE Main 2025, 2 April (Morning Shift)

Let A be the set of all functions f : Z Z and R be a relation on A such that R = \(f, g) : f(0) = g(1) and f(1) = g(0)\. Then R is :

  1. Symmetric and transitive but not reflexive
  2. Symmetric but neither reflexive nor transitive
  3. Transitive but neither reflexive nor symmetric
  4. Reflexive but neither symmetric nor transitive
Ques. 3JEE Main 2025, 29 January (Morning Shift)

Define a relation R on the interval [0, 2 ) by x R y if and only if 2 x - 2 y = 1. Then R is :

  1. both reflexive and symmetric but not transitive
  2. both reflexive and transitive but not symmetric
  3. reflexive but neither symmetric nor transitive
  4. an equivalence relation
Ques. 4JEE Main 2025, 28 January (Morning Shift)

If f(x) = 2x2x + 2, x R, then k=181 f ( k82 ) is equal to

  1. 82
  2. 81 2
  3. 41
  4. 812
Ques. 5JEE Main 2025, 28 January (Morning Shift)

The relation R = \(x, y) : x, y Z and x + y is even\ is:

  1. reflexive and transitive but not symmetric
  2. reflexive and symmetric but not transitive
  3. an equivalence relation
  4. symmetric and transitive but not reflexive
Ques. 6JEE Main 2025, 28 January (Evening Shift)

Let f: R - \0\ (- , 1) be a polynomial of degree 2, satisfying f(x)f ( 1x ) = f(x) + f ( 1x ). If f(K) = -2K, then the sum of squares of all possible values of K is:

  1. 9
  2. 1
  3. 6
  4. 7
Ques. 7JEE Main 2025, 28 January (Evening Shift)

Let f : [0, 3] A be defined by f(x) = 2x3 - 15x2 + 36x + 7 and g : [0, ) B be defined by g(x) = x2025x2025 + 1. If both the functions are onto and S = \x Z; x A or x B\, then n(S) is equal to :

  1. 29
  2. 31
  3. 30
  4. 36
Ques. 8JEE Main 2025, 24 January (Morning Shift)

Let f:R-\0\ be a function such that f(x)-6f ( 1x )= 353x- 52. If x 0 ( 1 x+f(x) )= ; , , then +2 is equal to

  1. 6
  2. 5
  3. 3
  4. 4
Ques. 9JEE Main 2025, 24 January (Morning Shift)

Let f(x)= 2x+2+1622x+1+2x+4+32. Then the value of 8 (f ( 115 )+f ( 215 )+ +f ( 5915 ) ) is equal to

  1. 108
  2. 92
  3. 118
  4. 102
Ques. 10JEE Main 2025, 24 January (Evening Shift)

The function f:(- , ) (- ,1), defined by f(x)= 2x-2-x2x+2-x is :

  1. One-one but not onto
  2. Onto but not one-one
  3. Both one-one and onto
  4. Neither one-one nor onto
Ques. 11JEE Main 2025, 24 January (Evening Shift)

Number of functions f:\1,2, ,100\ \0,1\, that assign 1 to exactly one of the positive integers less than or equal to 98, is equal to .

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