If A = [−4, 2) ∪ (5, 9] and B = (−1, 6], what is A \ B?
Answer and explanation
Correct answer: [−4, −1] ∪ (6, 9]
To find A \ B, retain points of A that do not belong to B. From [−4, 2), remove (−1, 2), but −1 remains because B is open at −1; this leaves [−4, −1]. From (5, 9], remove (5, 6], including 6 because B contains 6; this leaves (6, 9]. Hence A \ B = [−4, −1] ∪ (6, 9].
Frequently asked questions
What is the correct answer to this question?
[−4, −1] ∪ (6, 9]
Why is this the correct answer?
To find A \ B, retain points of A that do not belong to B. From [−4, 2), remove (−1, 2), but −1 remains because B is open at −1; this leaves [−4, −1]. From (5, 9], remove (5, 6], including 6 because B contains 6; this leaves (6, 9]. Hence A \ B = [−4, −1] ∪ (6, 9].
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).