Set Theory Help: Proving E C ]0,2] and Exploring Its Relationship with ]0,2]

In summary, the conversation was about proving that the set E, defined as {(a+b)/(ab): a,b positive integers}, is a subset of the interval ]0,2]. The conversation also delved into clarifying the notation used and discussing potential solutions using words and mathematical symbols. The final conclusion was that it is easy to prove that ]0,2] is a subset of E.
  • #1
Andrax
117
0
we have E=(a+b)/ab (a,b)EN*
1/ prove that E C ]0,2] (i already duid that )
2/ is ]0,2] E E? shelp me in this one!


Homework Equations





The Attempt at a Solution


x [itex]\in[/itex] ]0,2] [itex]\Rightarrow[/itex] x [itex]\in[/itex] E
 
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  • #2
Andrax said:
we have E=(a+b)/ab (a,b)EN*
1/ prove that E C ]0,2] (i already duid that )
2/ is ]0,2] E E? shelp me in this one!


Homework Equations





The Attempt at a Solution


x [itex]\in[/itex] ]0,2] [itex]\Rightarrow[/itex] x [itex]\in[/itex] E

If E=(a+b)/ab what does EN* mean? What does ]0,2]E E mean? Please state your problem with proper notation.
 
  • #3
LCKurtz said:
If E=(a+b)/ab what does EN* mean?
E means ##\in## and N* means the positive integers, I believe.
LCKurtz said:
What does ]0,2]E E mean? Please state your problem with proper notation.
I second that.
 
  • #4
well sorry didn't find the proper notations in the advanced mode umm any solution?
 
  • #5
Andrax said:
well sorry didn't find the proper notations in the advanced mode umm any solution?

You can use ε in the top row of Quick Symbols (on the right after you click Go Advanced). Or you can use LaTeX: [ itex ] \in [ /itex ] (without the spaces).

Also, tell us what you meant by N*.
 
  • #6
Andrax said:
well sorry didn't find the proper notations in the advanced mode umm any solution?

You could try using words:
E = {(a+b)/(ab): a,b positive integers}. And "is ]0,2] a subset of E?"
or
E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"

RGV
 
  • #7
Ray Vickson said:
You could try using words:
E = {(a+b)/(ab): a,b positive integers}. And "is ]0,2] a subset of E?"
or
E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"

RGV

I want to prove that ]0,2 is a subset of E E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"
 
  • #8
Aren't all the numbers in E rational?
 
  • #9
Andrax said:
I want to prove that ]0,2 is a subset of E E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"
In other words, you want to show that if [itex]0< x\le 2[/itex], the x= (a+ b)/(ab) for some positive integers a and b. [itex]\sqrt{2}[/itex] lies between 0 and 2 doesn't it?
 
  • #10
HallsofIvy said:
In other words, you want to show that if [itex]0< x\le 2[/itex], the x= (a+ b)/(ab) for some positive integers a and b. [itex]\sqrt{2}[/itex] lies between 0 and 2 doesn't it?

yes it does what's your point?
 
  • #11
ohh i get your point wow that's really easy don't know how i missed it
 

What is set theory?

Set theory is a branch of mathematics that deals with the study of sets, which are collections of objects or elements. It provides a foundation for all of mathematics and is used to define and analyze concepts such as numbers, relations, functions, and infinity.

What is a set?

A set is a well-defined collection of objects or elements. These objects can be anything, such as numbers, letters, or even other sets. Sets are typically denoted by curly braces { } and each element is separated by a comma. For example, the set of even numbers can be written as {2, 4, 6, 8, ...}.

What are the basic operations in set theory?

The three basic operations in set theory are union, intersection, and complement. Union combines all the elements from two or more sets, intersection finds the common elements between two or more sets, and complement finds all the elements that are not in a given set.

What is the difference between a set and a subset?

A set is a collection of elements, while a subset is a set that contains some or all of the elements of another set. In other words, all the elements of a subset are also elements of the larger set, but not all elements of the larger set are necessarily in the subset.

What are some real-life applications of set theory?

Set theory has numerous applications in various fields such as computer science, linguistics, and statistics. It is used in database management, programming languages, and natural language processing. In statistics, set theory is used to define probability and in linguistics, it is used to study language structure and grammar.

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