If the universal set is U = R and A = {x ∈ R : |x + 1| ≥ 4}, what is A'?
Answer and explanation
Correct answer: (-5, 3)
The inequality |x + 1| ≥ 4 means x + 1 ≤ -4 or x + 1 ≥ 4. Therefore A = (-∞, -5] ∪ [3, ∞). Since the universal set is R, its complement consists of the real numbers strictly between -5 and 3: A' = (-5, 3). The endpoints are excluded because they belong to A.
Frequently asked questions
What is the correct answer to this question?
(-5, 3)
Why is this the correct answer?
The inequality |x + 1| ≥ 4 means x + 1 ≤ -4 or x + 1 ≥ 4. Therefore A = (-∞, -5] ∪ [3, ∞). Since the universal set is R, its complement consists of the real numbers strictly between -5 and 3: A' = (-5, 3). The endpoints are excluded because they belong to A.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Complement of a Set and Its Properties.