Math Help Sets
July 26th, 2010
Question: Discrete math question about sets?
I’m running through some homework and am stuck on a problem:
What can you say about the sets A and B if the following are true?
(a) A – B = A
(b) A – B = B – A
I don’t understand at all what sort of answer I’m supposed to give to these two questions and would appreciate help.
Answer: (a) A – B = A
You can say that no elements of A are in B, and that no elements in B are in A. I believe there’s a name for this property of a set, although currently I forget what it is.
(b) A – B = B – A
A – B = B – A
B and A are the exact same set, you can use a Venn diagram to confirm this, and it is a property of sets used to prove that sets are equal.
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