If A = {x : x ∈ ℕ and x is a square root of 16}, what is A?
Answer and explanation
Correct answer: {4}
The numbers whose square is 16 are 4 and −4, because 4² = 16 and (−4)² = 16. However, the condition specifies that x belongs to ℕ, the set of natural numbers. Under the usual school convention, −4 is not a natural number, so it must be excluded. Therefore the only member of A is 4, and A = {4}.
Frequently asked questions
What is the correct answer to this question?
{4}
Why is this the correct answer?
The numbers whose square is 16 are 4 and −4, because 4² = 16 and (−4)² = 16. However, the condition specifies that x belongs to ℕ, the set of natural numbers. Under the usual school convention, −4 is not a natural number, so it must be excluded. Therefore the only member of A is 4, and A = {4}.
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.