Which set is this picture explaining.
1.$A\cap B\cap C$
2.$(C-A) \cup (C-B)$
3.$(A-C) \cap (A-B)$
4.$C-((C-A) \cup(C-B))$
Our teacher give the answer $4$ but I wrote $1$. What's wrong with my answer?
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2$\begingroup$ 1 is the correct answer. $\endgroup$– T.J. GaffneyCommented Jul 5, 2016 at 14:46
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1$\begingroup$ There must be a printing error in the answer. Printers fail sometimes. $\endgroup$– Mc ChengCommented Jul 5, 2016 at 14:49
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$\begingroup$ Are you sure our teacher is an intellegent person. $\endgroup$– Taha AkbariCommented Jul 5, 2016 at 14:50
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1$\begingroup$ In this case, both 1 and 4 are correct... $\endgroup$– Mc ChengCommented Jul 5, 2016 at 14:52
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1$\begingroup$ There are a lot of impossible things in math. $\endgroup$– Ivan NeretinCommented Jul 5, 2016 at 15:11
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1 Answer
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1 and 4 are the correct answers. So what's wrong with your answer is that you did't say "1 and 4".
answered Jul 5, 2016 at 15:14
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$\begingroup$ No he says the answer is only $1$ $\endgroup$ Commented Jul 5, 2016 at 15:15
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$\begingroup$ Then his answer is also wrong. Are you sure answer 1 is not $A\cup B\cup C$? $\endgroup$ Commented Jul 5, 2016 at 15:16
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$\begingroup$ No it isn't.Also $1$ is better answer . $\endgroup$ Commented Jul 5, 2016 at 15:17
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1$\begingroup$ 1 is a simpler answer. "Better" is a subjective statement. If simpler is better then it is better. If demonstrating that complicated set membership statements can be equivalent to simple ones is desirable then answer 4 is better. The answer to the question posed above, is that the diagram is explaining the sets described in 1 and 4. $\endgroup$ Commented Jul 5, 2016 at 15:19
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$\begingroup$ @Qwerty the question is "Why was my answer wrong?" The answer to that question is "Your answer was wrong because the correct answer is '1 and 4' while your answer was '1'". Taha's answer is wrong because it was incomplete. So it exactly does provide an answer the question. $\endgroup$ Commented Jul 5, 2016 at 16:14