If A = {x ∈ R : x² + 4 = 0} and B = ∅, which statement is correct?
Answer and explanation
Correct answer: A = B
Because x is restricted to real numbers, x² is always non-negative. Consequently, x² + 4 is always at least 4 and can never equal zero. Thus the equation has no real solution, so A contains no elements and A = ∅. Since B is also given as the empty set, A and B are equal. Option A is therefore correct.
Frequently asked questions
What is the correct answer to this question?
A = B
Why is this the correct answer?
Because x is restricted to real numbers, x² is always non-negative. Consequently, x² + 4 is always at least 4 and can never equal zero. Thus the equation has no real solution, so A contains no elements and A = ∅. Since B is also given as the empty set, A and B are equal. Option A is therefore correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: The Empty Set, Finite and Infinite Sets, Equal Sets.