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MCQ practice · SSC Higher Mathematics Board questions · Chapter 1: Set and Function

Cumilla Board 2024

If f(x) = x², which of the following is correct?

  1. i. dom f = ℝ
  2. ii. range f = {y ∈ ℝ : y ≥ 0}
  3. iii. f is a one-one function

Think it through first, then pick an option.

  1. a i and ii
  2. b i and iii
  3. c ii and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: a i and ii

Any real x can be squared and squares are never negative; but f(−1) = f(1).

Why the other options are wrong

  • b i and iii: iii is false: f(−1) = f(1) = 1, so it is not one-one.
  • c ii and iii: iii is false (not one-one), while i is true: any real x works.
  • d i, ii and iii: iii is false: the different inputs −1 and 1 share the image 1.