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Relations and Functions (Class 12) · Question 9

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

If g(x) = 3x2 + 2x - 3, f(0) = -3 and 4g(f(x)) = 3x2 - 32x + 72, then f(g(2)) is equal to:

  1. 72
  2. - 256
  3. 256
  4. - 72

Answer

(1) 72

Solution

4g(f(x)) = 12f(x)2 + 8f(x) - 12 = 3x2 - 32x + 72

Degree 2 on the right f is linear: let f(x) = ax + b; f(0) = -3 b = -3

12(ax - 3)2 + 8(ax - 3) - 12

= 12a2x2 - 64ax + 72

Comparing with 3x2 - 32x + 72:

12a2 = 3 and 64a = 32 a = 12

f(x) = x2 - 3

g(2) = 12 + 4 - 3 = 13

f(g(2)) = f(13) = 132 - 3 = 72

Answer: (1)

JEE Main 2026 (Online) 28th January Morning Shift

Keep practising — Relations and Functions (Class 12)

2

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is true but Statement II is false
  2. Both Statement I and Statement II are false
  3. Both Statement I and Statement II are true
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 28th January Evening Shift
3

Let R be a relation defined on the set \1, 2, 3, 4\ \1, 2, 3, 4\ by R = \((a, b), (c, d)) : 2a + 3b = 3c + 4d\. Then the number of elements in R is

  1. 6
  2. 15
  3. 12
  4. 18
JEE Main 2026 (Online) 24th January Morning Shift
4

Let f be a function such that 3f(x) + 2f ( m19x ) = 5x, x 0, where m = i=19 (i)2. Then f(5) - f(2) is equal to

  1. 36
  2. 9
  3. -9
  4. 18
JEE Main 2026 (Online) 24th January Evening Shift
5

Let A = \-2, -1, 0, 1, 2, 3, 4\. Let R be a relation on A defined by xRy if and only if 2x + y 2. 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. 34
  2. 32
  3. 33
  4. 35
JEE Main 2026 (Online) 23rd January Morning Shift
6

Consider two sets A = \x Z : |(|x - 3| - 3)| 1\ and B = \x R - \1, 2\ : (x - 2)(x - 4)x - 1 e(|x - 2|) = 0 \. Then the number of onto functions f : A B is equal to :

  1. 32
  2. 81
  3. 79
  4. 62
JEE Main 2026 (Online) 23rd January Evening Shift
7

Let A = \0, 1, 2, , 9\. Let R be a relation on A defined by (x, y) R if and only if |x - y| is a multiple of 3. Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is correct but Statement II is incorrect
  2. Both Statement I and Statement II are correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is incorrect but Statement II is correct
JEE Main 2026 (Online) 23rd January Evening Shift
8

Let the relation R on the set M = \1, 2, 3, , 16\ be given by R = \(x, y) : 4y = 5x - 3, x, y M\. Then the minimum number of elements required to be added in R, in order to make the relation symmetric, is equal to

  1. 4
  2. 3
  3. 1
  4. 2
JEE Main 2026 (Online) 22nd January Morning Shift
9

Let f and g be functions satisfying f(x + y) = f(x)f(y), f(1) = 7 and g(x + y) = g(xy), g(1) = 1, for all x, y N. If x = 1n ( f(x)g(x) ) = 19607, then n is equal to :

  1. 6
  2. 7
  3. 4
  4. 5
JEE Main 2026 (Online) 22nd January Evening Shift
10

The number of strictly increasing functions f from the set \1, 2, 3, 4, 5, 6\ to the set \1, 2, 3, , 9\ such that f(i) i for 1 i 6, is equal to :

  1. 21
  2. 28
  3. 27
  4. 22
JEE Main 2026 (Online) 21st January Morning Shift
11

The number of relations, defined on the set \a, b, c, d\, which are both reflexive and symmetric, is equal to:

  1. 16
  2. 64
  3. 256
  4. 1024
JEE Main 2026 (Online) 21st January Morning Shift

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