#Prove/disprove subset

19 messages · Page 1 of 1 (latest)

rich marlin
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Able to get till A' ∪ (B ∪ C) with set difference and De Morgan's law, but that's different from the right hand side...
Perhaps the statement is false but also not sure how to disprove...

autumn oasisBOT
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sharp sail
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Well for any set A and B A\B= A ∩ Comp(B)

sharp sail
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Then you can maybe use Morgan’s formula

jagged cairn
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$\overline{A\setminus\qty(B\cup C)}=\overline{A\cap\overline{\qty(B\cup C)}}$

hoary pelicanBOT
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Romans 12:19

jagged cairn
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im not supposed to throw solutions lmao

jagged cairn
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remember the complement of an intersection?

rich marlin
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Yes, I got A' ∪ (B ∪ C) with set difference and De Morgan's law, but the right hand side is A' ∩ (B ∪ C)...
See the union and intersect after A' is different.

rich marlin
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So I can directly say because it's different, it's disproved? Somehow seems too simple for a 5 marks qns...

jagged cairn
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give a counterexample too if u like\

rich marlin
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Not sure how counter example for set theory looks like, my prof haven't shown any counter examples etc so far... All he ever said was to prove a subset, just show that everything in the first set is in the second set and that's all...

jagged cairn
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i mean, it'd suffice to say that the equality doesn't hold true always since intersection and union are different operations.
a counterexample'd work like: we may find anyy 3 sets A,B,C that do not satisfy the equation, thus it does not hold for all the A,B,C it claims to hold for

rich marlin
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I see, I guess I'll say they don't equate due to the operations. Thanks for explaining!

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