If Y = {x : x ∈ ℤ, x² < 4}, how many elements does Y have?
Answer and explanation
Correct answer: 3
For integers, x² < 4 means |x| < 2, or equivalently −2 < x < 2. The integers strictly between −2 and 2 are −1, 0, and 1. Thus Y = {−1, 0, 1}, which contains three elements. The endpoints −2 and 2 are excluded because the inequality is strict, using < rather than ≤.
Frequently asked questions
What is the correct answer to this question?
3
Why is this the correct answer?
For integers, x² < 4 means |x| < 2, or equivalently −2 < x < 2. The integers strictly between −2 and 2 are −1, 0, and 1. Thus Y = {−1, 0, 1}, which contains three elements. The endpoints −2 and 2 are excluded because the inequality is strict, using < rather than ≤.
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.