If F₁ = {x : x ∈ ℝ and x² + 4 = 0}, what is F₁?
Answer and explanation
Correct answer: Empty set
For every real number x, x² is at least 0. Consequently, x² + 4 is at least 4, so it can never equal 0. Equivalently, the equation would require x² = −4, which has no real solution. Since F₁ contains real numbers satisfying the condition and there are none, F₁ = ∅, the empty set.
Frequently asked questions
What is the correct answer to this question?
Empty set
Why is this the correct answer?
For every real number x, x² is at least 0. Consequently, x² + 4 is at least 4, so it can never equal 0. Equivalently, the equation would require x² = −4, which has no real solution. Since F₁ contains real numbers satisfying the condition and there are none, F₁ = ∅, the empty set.
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.