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Relations and Functions (Class 12) · Question 36

JEE Main 2025 (Online) 28th January Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
1

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

Answer

(3) 30

Solution

Since f and g are onto, A = range of f and B = range of g.

f'(x) = 6x2 - 30x + 36 = 6(x - 2)(x - 3)

f increases on [0, 2] and decreases on [2, 3].

f(0) = 7, f(2) = 16 - 60 + 72 + 7 = 35, f(3) = 54 - 135 + 108 + 7 = 34

A = [7, 35] integers 7, 8, …, 35: 29 integers

g(x) = 1 - 1x2025 + 1 increases from g(0) = 0 towards 1 (never reaching 1)

B = [0, 1) only integer 0

n(S) = 29 + 1 = 30

Answer: (3)

JEE Main 2025 (Online) 28th January Evening Shift

Keep practising — Relations and Functions (Class 12)

2

Consider the relation R on the set \-2, -1, 0, 1, 2\ defined by (a, b) R if and only if 1+ab>0. Then, among the statements :

  1. Only I is true
  2. Only II is true
  3. Both I and II are true
  4. Neither I nor II is true
JEE Main 2026 (Online) 8th April Evening Shift
3

Let f be a polynomial function such that 2(f(x))= ( 2 (2+ 23+ 29+ ) ) 3 (1+ f(x)f ( 1x ) ), x>0 and f(6)=37. Then n=110f(n) is equal to .

JEE Main 2026 (Online) 8th April Evening Shift
4

Let f: R R be defined as f(x)= 2x2-3x+23x2+x+3. Then f is :

  1. both one-one and onto
  2. one-one but not onto
  3. onto but not one-one
  4. neither one-one nor onto
JEE Main 2026 (Online) 6th April Evening Shift
5

Let R= \(x, y) N N : e(x+y) 2 \. Then the minimum number of elements, required to be added in R to make it a transitive relation, is .

JEE Main 2026 (Online) 6th April Evening Shift
6

Let A=\1, 2, 3, 4, 5, 6\. The number of one-one functions f : A A such that f(1) 3, f(3) 4 and f(2)+f(3)=5, is .

JEE Main 2026 (Online) 5th April Morning Shift
7

The number of functions f : \1, 2, 3, 4\ \a, b, c\, which are not onto, is :

  1. 48
  2. 45
  3. 51
  4. 35
JEE Main 2026 (Online) 4th April Morning Shift
8

For the function f : [1, ) [1, ) defined by f(x)=(x-1)4+1, among the two statements : (I) The set S=\x [1, ) : f(x)=f-1(x)\ contains exactly two elements, and (II) The set S=\x [1, ) : f(x)=f-1(x+1)\ is an empty set,

  1. only (I) is TRUE
  2. only (II) is TRUE
  3. both (I) and (II) are TRUE
  4. neither (I) nor (II) is TRUE
JEE Main 2026 (Online) 4th April Evening Shift
9

Let for some R, f : R R be a function satisfying f(x+y)=f(x)+2y2+y+ xy for all x, y R. If f(0)=-1 and f(1)=2, then the value of n=15 ( +f(n) ) is :

  1. 110
  2. 140
  3. 150
  4. 170
JEE Main 2026 (Online) 4th April Evening Shift
10

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
JEE Main 2026 (Online) 28th January Morning Shift
11

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

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