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Relations and Functions (Class 12) · Question 20

JEE Main 2026 (Online) 21st January Evening ShiftMCQMedium📈 Topic in 45% papers+4−1
1

Let A = \2, 3, 5, 7, 9\. Let R be the relation on A defined by xRy if and only if 2x 3y. Let l be the number of elements in R, and m be the minimum number of elements required to be added in R to make it a symmetric relation. Then l + m is equal to:

  1. 21
  2. 25
  3. 23
  4. 27

Answer

(2) 25

Solution

(x, y) R y 2x3

x = 2: y 43 y = 2, 3, 5, 7, 9 (5 pairs)

x = 3: y 2 y = 2, 3, 5, 7, 9 (5 pairs)

x = 5: y 103 y = 5, 7, 9 (3 pairs)

x = 7: y 143 y = 5, 7, 9 (3 pairs)

x = 9: y 6 y = 7, 9 (2 pairs)

l = 5 + 5 + 3 + 3 + 2 = 18

For symmetry, (y, x) must be added for every (x, y) R with (y, x) R:

(2, 5), (2, 7), (2, 9) R but (5, 2), (7, 2), (9, 2) R 3 pairs

(3, 5), (3, 7), (3, 9) R but (5, 3), (7, 3), (9, 3) R 3 pairs

(5, 9) R but (9, 5) R 1 pair

(Pairs among 5, 7, 9 other than these, and (2, 3), (3, 2), are already symmetric.)

m = 7

l + m = 18 + 7 = 25

Answer: (2)

JEE Main 2026 (Online) 21st January Evening Shift

Keep practising — Relations and Functions (Class 12)

2

Let A = \0, 1, 2, 3, 4, 5\. Let R be a relation on A defined by (x, y) R if and only if \x, y\ \3, 4\. Then among the statements (S1): The number of elements in R is 18, and (S2): The relation R is symmetric but neither reflexive nor transitive

  1. both are false
  2. only (S1) is true
  3. only (S2) is true
  4. both are true
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3

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4

Let f : R R be a continuous function satisfying f(0) = 1 and f(2x) - f(x) = x for all x R. If n \f(x) - f ( x2n ) \ = G(x), then r=110 G (r2 ) is equal to

  1. 215
  2. 420
  3. 385
  4. 540
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5

Consider the sets A = \(x, y) R R : x2 + y2 = 25 \, B = \(x, y) R R : x2 + 9y2 = 144 \, C = \(x, y) Z Z : x2 + y2 4 \ and D = A B. The total number of one-one functions from the set D to the set C is:

  1. 15120
  2. 18290
  3. 17160
  4. 19320
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6

Let f, g : (1, ) R be defined as f(x) = 2x + 35x + 2 and g(x) = 2 - 3x1 - x. If the range of the function f g : [2, 4] R is [ , ], then 1 - is equal to

  1. 56
  2. 2
  3. 29
  4. 68
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7

Let A = \-3, -2, -1, 0, 1, 2, 3\ and R be a relation on A defined by xRy if and only if 2x - y \0, 1\. Let l be the number of elements in R. Let m and n be the minimum number of elements required to be added in R to make it reflexive and symmetric relations, respectively. Then l + m + n is equal to:

  1. 17
  2. 18
  3. 15
  4. 16
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8

Let A = \-3, -2, -1, 0, 1, 2, 3\. Let R be a relation on A defined by x R y if and only if 0 x2 + 2y 4. Let l be the number of elements in R and m be the minimum number of elements required to be added in R to make it a reflexive relation. Then l + m is equal to

  1. 18
  2. 20
  3. 17
  4. 19
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9

Let f be a function such that f(x) + 3f ( 24x ) = 4x, x 0. Then f(3) + f(8) is equal to

  1. 13
  2. 11
  3. 10
  4. 12
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10

Let A = \-2, -1, 0, 1, 2, 3\. Let R be a relation on A defined by xRy if and only if y = \x, 1\. Let l be the number of elements in R. Let m and n be the minimum number of elements required to be added in R to make it reflexive and symmetric relations, respectively. Then l + m + n is equal to

  1. 11
  2. 12
  3. 14
  4. 13
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11

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
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