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CA Foundation · Quantitative Aptitude · Sets, Relations and Functions, Limits and Continuity

Which of the following sets is an empty (null) set?

The set of real numbers satisfying x² + 1 = 0 is empty because a real square cannot be negative. The other sets contain elements: {-2, 2}, {0} and {1}.

  1. A{x : x is a real number and x² + 1 = 0}Correct
  2. B{x : x is an integer and x² = 4}
  3. C{0}
  4. D{x : x is a natural number and x < 2}

Explanation

x² + 1 = 0 has no real solution since x² ≥ 0. Option 2 gives {-2, 2}. {0} has one element, zero. Option 4 gives {1}.

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