If A = {x ∈ R : x² + 1 = 0}, what is A as a subset of the real numbers?
Answer and explanation
Correct answer: ∅
For every real number x, x² is non-negative, so x² + 1 is at least 1 and can never equal zero. Consequently, the defining condition has no real solution, and A contains no elements. Therefore A is the empty set ∅. The values i and −i solve the equation only in the complex number system, not in R.
Frequently asked questions
What is the correct answer to this question?
∅
Why is this the correct answer?
For every real number x, x² is non-negative, so x² + 1 is at least 1 and can never equal zero. Consequently, the defining condition has no real solution, and A contains no elements. Therefore A is the empty set ∅. The values i and −i solve the equation only in the complex number system, not in R.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Power Set and Subsets.