Interval - when to add ( ) or [ ]

Aufrufe: 236     Aktiv: 02.11.2023 um 12:43

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Hello,

reason why I have decided to write is because I am currently learning Intervals and don't understand when you add ( ) or [ ]. I understand () is for open intervals, [ ] is for closed, but when task includes mixed brackets....well for me represents the problem. I am kindly asking for help actually if someone could explain me for these two examples on pictures, where it says to write down for union and intersection interval because I still do not understand final results (why is it in first example the result (-1 ,0) and not [-1,0] or something else, as well why is it in second example the result everything although there is a gap between 3 and 5).

Thank you

PS: Tasks are in Slovenian language because I am from Slovenia :D




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1. The intersection of two sets consists of all points that are in both sets, set1 and set2. -1 is not contained in set2, therefore not in the intersection.
2. I don't understand what the problem here is.
In your question do state the problem precisely, in German or English, in the original form (translated) - what is given, what precisely is the task.
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1. I still unfortunately do not understand the result for the first solution, why -1 is not included, because in set1 it is, right? What do I have to look (arrows, dots) to understand the final result which is (-1, 0)? Not just asking specifically for this task but in general for further tasks.

2. About second question. I do not understand why is the result of [-2,3 ] U [5, 7] actually the final result as it is the task, I know what is the meaning of union (it contains everything), but for me it is not understandable as you can see on picture there is a gap between 3 and 5, there is nothing, so how it can be union?
  ─   ariana.maksi23 01.11.2023 um 17:48

You should repeat the basics in sets, as you don't understand what intersection and union means. It's related to logical "and" and "or". When you really understand these, read my answer above again.   ─   mikn 01.11.2023 um 18:22

Good, I am going to repeat as you said. Thank you.   ─   ariana.maksi23 02.11.2023 um 12:43

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