Prove that if $a<A$ and $b<B$ then $a+b<A+B$ [closed]

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From the axioms from which $ℝ$ is usually constructed, how could one prove that for all $a, b, A, B in ℝ$ if $$a<A$$ and $$b<B$$ then $$a+b<A+B$$




Any help/thoughts would be really appreciated.







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closed as off-topic by Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne Aug 2 at 21:05


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne
If this question can be reworded to fit the rules in the help center, please edit the question.








  • 5




    If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
    – Doug M
    Aug 1 at 20:02










  • @DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
    – Taroccoesbrocco
    Aug 1 at 20:07














up vote
-1
down vote

favorite












From the axioms from which $ℝ$ is usually constructed, how could one prove that for all $a, b, A, B in ℝ$ if $$a<A$$ and $$b<B$$ then $$a+b<A+B$$




Any help/thoughts would be really appreciated.







share|cite|improve this question











closed as off-topic by Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne Aug 2 at 21:05


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne
If this question can be reworded to fit the rules in the help center, please edit the question.








  • 5




    If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
    – Doug M
    Aug 1 at 20:02










  • @DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
    – Taroccoesbrocco
    Aug 1 at 20:07












up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











From the axioms from which $ℝ$ is usually constructed, how could one prove that for all $a, b, A, B in ℝ$ if $$a<A$$ and $$b<B$$ then $$a+b<A+B$$




Any help/thoughts would be really appreciated.







share|cite|improve this question











From the axioms from which $ℝ$ is usually constructed, how could one prove that for all $a, b, A, B in ℝ$ if $$a<A$$ and $$b<B$$ then $$a+b<A+B$$




Any help/thoughts would be really appreciated.









share|cite|improve this question










share|cite|improve this question




share|cite|improve this question









asked Aug 1 at 19:57









Leo

687416




687416




closed as off-topic by Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne Aug 2 at 21:05


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne
If this question can be reworded to fit the rules in the help center, please edit the question.




closed as off-topic by Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne Aug 2 at 21:05


This question appears to be off-topic. The users who voted to close gave this specific reason:


  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Jyrki Lahtonen, Simply Beautiful Art, John Ma, José Carlos Santos, Isaac Browne
If this question can be reworded to fit the rules in the help center, please edit the question.







  • 5




    If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
    – Doug M
    Aug 1 at 20:02










  • @DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
    – Taroccoesbrocco
    Aug 1 at 20:07












  • 5




    If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
    – Doug M
    Aug 1 at 20:02










  • @DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
    – Taroccoesbrocco
    Aug 1 at 20:07







5




5




If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
– Doug M
Aug 1 at 20:02




If you add the same thing to both sides of an equality the inequality holds. $A>a implies A+B > a + B$ and $B>b implies a + B > a+ b$ and inequality is transitive. $A+B > a + B > a+b$
– Doug M
Aug 1 at 20:02












@DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
– Taroccoesbrocco
Aug 1 at 20:07




@DougM - I was writing the same thing as you, but you have been faster than me. I think you should post it as an answer.
– Taroccoesbrocco
Aug 1 at 20:07










1 Answer
1






active

oldest

votes

















up vote
0
down vote













We have



  • $a<Aimplies A-a>0$


  • $b<Bimplies B-b>0$


therefore



$$A-a+B-b>B-b>0implies A-a+B-b>0 implies a+b<A+B$$






share|cite|improve this answer



















  • 1




    But, question was to use the axioms stated in the link. I don't think this approach does that
    – Rumpelstiltskin
    Aug 1 at 20:08






  • 1




    @gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
    – Leo
    Aug 1 at 20:09










  • @Adam Now it should be fixed! Thanks
    – gimusi
    Aug 1 at 21:09










  • @Leo Now it should be more clear.
    – gimusi
    Aug 1 at 21:10

















1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
0
down vote













We have



  • $a<Aimplies A-a>0$


  • $b<Bimplies B-b>0$


therefore



$$A-a+B-b>B-b>0implies A-a+B-b>0 implies a+b<A+B$$






share|cite|improve this answer



















  • 1




    But, question was to use the axioms stated in the link. I don't think this approach does that
    – Rumpelstiltskin
    Aug 1 at 20:08






  • 1




    @gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
    – Leo
    Aug 1 at 20:09










  • @Adam Now it should be fixed! Thanks
    – gimusi
    Aug 1 at 21:09










  • @Leo Now it should be more clear.
    – gimusi
    Aug 1 at 21:10














up vote
0
down vote













We have



  • $a<Aimplies A-a>0$


  • $b<Bimplies B-b>0$


therefore



$$A-a+B-b>B-b>0implies A-a+B-b>0 implies a+b<A+B$$






share|cite|improve this answer



















  • 1




    But, question was to use the axioms stated in the link. I don't think this approach does that
    – Rumpelstiltskin
    Aug 1 at 20:08






  • 1




    @gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
    – Leo
    Aug 1 at 20:09










  • @Adam Now it should be fixed! Thanks
    – gimusi
    Aug 1 at 21:09










  • @Leo Now it should be more clear.
    – gimusi
    Aug 1 at 21:10












up vote
0
down vote










up vote
0
down vote









We have



  • $a<Aimplies A-a>0$


  • $b<Bimplies B-b>0$


therefore



$$A-a+B-b>B-b>0implies A-a+B-b>0 implies a+b<A+B$$






share|cite|improve this answer















We have



  • $a<Aimplies A-a>0$


  • $b<Bimplies B-b>0$


therefore



$$A-a+B-b>B-b>0implies A-a+B-b>0 implies a+b<A+B$$







share|cite|improve this answer















share|cite|improve this answer



share|cite|improve this answer








edited Aug 1 at 20:12


























answered Aug 1 at 20:05









gimusi

63.9k73480




63.9k73480







  • 1




    But, question was to use the axioms stated in the link. I don't think this approach does that
    – Rumpelstiltskin
    Aug 1 at 20:08






  • 1




    @gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
    – Leo
    Aug 1 at 20:09










  • @Adam Now it should be fixed! Thanks
    – gimusi
    Aug 1 at 21:09










  • @Leo Now it should be more clear.
    – gimusi
    Aug 1 at 21:10












  • 1




    But, question was to use the axioms stated in the link. I don't think this approach does that
    – Rumpelstiltskin
    Aug 1 at 20:08






  • 1




    @gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
    – Leo
    Aug 1 at 20:09










  • @Adam Now it should be fixed! Thanks
    – gimusi
    Aug 1 at 21:09










  • @Leo Now it should be more clear.
    – gimusi
    Aug 1 at 21:10







1




1




But, question was to use the axioms stated in the link. I don't think this approach does that
– Rumpelstiltskin
Aug 1 at 20:08




But, question was to use the axioms stated in the link. I don't think this approach does that
– Rumpelstiltskin
Aug 1 at 20:08




1




1




@gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
– Leo
Aug 1 at 20:09




@gimusi. I can see how $a-A<0>b-B$. However, how did you get to $a-A+b-B<0$?
– Leo
Aug 1 at 20:09












@Adam Now it should be fixed! Thanks
– gimusi
Aug 1 at 21:09




@Adam Now it should be fixed! Thanks
– gimusi
Aug 1 at 21:09












@Leo Now it should be more clear.
– gimusi
Aug 1 at 21:10




@Leo Now it should be more clear.
– gimusi
Aug 1 at 21:10


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