If A = {x ∈ R : 1 ≤ x ≤ 9} and B = {x ∈ R : 3 < x < 7}, what is A − B?
Answer and explanation
Correct answer: [1, 3] ∪ [7, 9]
A is the closed interval [1, 9], while B is the open interval (3, 7). To find A − B, remove every real number strictly between 3 and 7 from A. The endpoints 3 and 7 are not elements of B because B uses strict inequalities, so they remain. The result is [1, 3] ∪ [7, 9].
Frequently asked questions
What is the correct answer to this question?
[1, 3] ∪ [7, 9]
Why is this the correct answer?
A is the closed interval [1, 9], while B is the open interval (3, 7). To find A − B, remove every real number strictly between 3 and 7 from A. The endpoints 3 and 7 are not elements of B because B uses strict inequalities, so they remain. The result is [1, 3] ∪ [7, 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).