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Relations and Functions (Class 12) · Question 33

JEE Main 2025 (Online) 28th January Morning ShiftMCQEasy📈 Topic in 29% papers+4−1
1

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

  1. 82
  2. 81 2
  3. 41
  4. 812

Answer

(4) 812

Solution

f(1 - x) = 21-x21-x + 2 = 22 + 2 2x = 2 2 + 2x

f(x) + f(1 - x) = 2x + 22x + 2 = 1

Pair the terms k and 82 - k: f ( k82 ) + f ( 82 - k82 ) = 1, for k = 1, 2, , 40 40 pairs.

Middle term: f ( 4182 ) = f ( 12 ) = 2 2 + 2 = 12

Sum = 40 + 12 = 812

Answer: (4)

JEE Main 2025 (Online) 28th January Morning Shift

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2

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
JEE Main 2025 (Online) 28th January Morning Shift
3

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
JEE Main 2025 (Online) 28th January Evening Shift
4

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
JEE Main 2025 (Online) 28th January Evening Shift

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