Proving (A-B) U C ≤ (A U B U C) - (A n B)

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Homework Help Overview

The problem involves proving the set relationship (A - B) U C ⊆ (A U B U C) - (A ∩ B), which pertains to set theory and the properties of unions and intersections of sets.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss starting points for the proof, including examining the elements of the sets involved. Some express uncertainty about the correct notation and terminology for sets. Others suggest considering counterexamples to explore the validity of the statement.

Discussion Status

The discussion is ongoing, with participants sharing their attempts and questioning the clarity of the problem statement. Some guidance has been offered regarding the use of set notation, but no consensus has been reached on the approach to take.

Contextual Notes

There is a noted confusion regarding the use of symbols and terminology, particularly the distinction between set relationships and numerical comparisons. Additionally, the professor's suggestion to consider counterexamples introduces an element of exploration into the discussion.

taylor81792
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Homework Statement


The problem I have been given is to prove (A - B) U C is than less or equal to (A U B U C) - (A n B)

The Attempt at a Solution


I've tried starting off with just (A-B) U C. Then I would say how x ε c or x ε (A - B). Also if x ε a, then x ε c and x is not in b. If x ε c, since c is a subset of (A U B U C) , x ε (A U B U C). I don't know if this is right or where to go from here.
 
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taylor81792 said:

Homework Statement


The problem I have been given is to prove (A - B) U C is than less or equal to (A U B U C) - (A n B)
This is a statement about sets, so the relationship is \subseteq, not ≤.
taylor81792 said:

The Attempt at a Solution


I've tried starting off with just (A-B) U C. Then I would say how x ε c or x ε (A - B). Also if x ε a, then x ε c and x is not in b.
Try to be more careful with the names of the sets, which are A, B, and C, not a, b, and c.
taylor81792 said:
If x ε c, since c is a subset of (A U B U C) , x ε (A U B U C). I don't know if this is right or where to go from here.
 
i'd say that u can use:

AUBUC= lAl + lBl + lCl - lBnCl - lAnBl - lAnCl+lAnBnCl

but I'm not 100% positive just trying to give some help :)
 
My professor said we can also try to prove or find a counterexample to this statement. Let A, B and C be sets. Then (A-B) U C = (A U B U C) - (A n B). I'm not really sure what she means by counterexample.
 
mtayab1994 said:
i'd say that u can use:

AUBUC= lAl + lBl + lCl - lBnCl - lAnBl - lAnCl+lAnBnCl

but I'm not 100% positive just trying to give some help :)
Not only does that not help, it makes no sense. The left side is a set, the right side is a number.

Even if you meant |AUBUC| that is irrelevant to the problem. Showing that two sets have the same size does not prove they are the same set.
 

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