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Showing why $Bbb Z^-∩Bbb Z^+=∅$ is true


Addition of cardinalitiesProving relation $(x,y)in Bbb RtimesBbb Rmid y = x^2$ is not a transitive relationConfusion about the null (empty) set being contained in other setsProvide a counter example to the claim that "for every set S, if ∅∈P(S) , then ∅∈SProviding counterexamples to the claim: If $|A cap B| < |A|$ then $|A|>|B|$How to show that $bigcup_ninBbb Nleft[0,1-frac 1nright]=[0,1)$?Proving True or False, Set QuestionHow do you prove the statement: $P(A cap B)=P(A) cap P(B)$If $A^X$ is equipotent to $B^X$ does it imply that A is equipotent to B?A Countable Well-ordered (w.r.to usual order) subset of $BbbR$ which is not of same order type with a subset of $BbbN$













1












$begingroup$



My Problem: Is this statement true or false? Give a reason. If false a counter example is adequate.
$$Bbb Z^-∩Bbb Z^+=∅$$




I'm more so after the reasoning as I don't know how to word it. I know the statement is true.










share|cite|improve this question











$endgroup$
















    1












    $begingroup$



    My Problem: Is this statement true or false? Give a reason. If false a counter example is adequate.
    $$Bbb Z^-∩Bbb Z^+=∅$$




    I'm more so after the reasoning as I don't know how to word it. I know the statement is true.










    share|cite|improve this question











    $endgroup$














      1












      1








      1





      $begingroup$



      My Problem: Is this statement true or false? Give a reason. If false a counter example is adequate.
      $$Bbb Z^-∩Bbb Z^+=∅$$




      I'm more so after the reasoning as I don't know how to word it. I know the statement is true.










      share|cite|improve this question











      $endgroup$





      My Problem: Is this statement true or false? Give a reason. If false a counter example is adequate.
      $$Bbb Z^-∩Bbb Z^+=∅$$




      I'm more so after the reasoning as I don't know how to word it. I know the statement is true.







      elementary-set-theory






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Mar 30 at 0:15









      Andrés E. Caicedo

      65.9k8160252




      65.9k8160252










      asked Mar 29 at 3:44









      JMWJMW

      62




      62




















          2 Answers
          2






          active

          oldest

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          4












          $begingroup$

          I don't really think there is any particularly "elegant" logic needed - simply that they don't share a common element. It basically amounts to "there is no integer which is both positive and negative."



          I guess if you want to argue it in a somewhat formal way, you can say that, for all $n in Bbb Z^-$, $n < 0$, and for all $m in Bbb Z^+$, $m > 0$. If there exists an element $k$ in the intersection of the two, this means $k<0$, but also $k>0$, which is simply not possible.






          share|cite|improve this answer









          $endgroup$




















            0












            $begingroup$

            An intersection of two sets is the set of elements that are in both sets.



            $mathbb Z^+$ is the set of integers that are positive and $mathbb Z^-$ is the set of integer that are negative. So $mathbb Z^+ cap mathbb Z^+$ are the set of integers that are both positive and negative.



            To be negative is to be less than $0$ and to be positive is to be bigger than $0$. A fundamental principal of real numbers is that for any $a,b$ either $a < b; a=b$ or $a > b$-- exactly one and only one of those is true. So an integer being both greater than and less than $0$ is impossible.






            share|cite|improve this answer









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              2 Answers
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              4












              $begingroup$

              I don't really think there is any particularly "elegant" logic needed - simply that they don't share a common element. It basically amounts to "there is no integer which is both positive and negative."



              I guess if you want to argue it in a somewhat formal way, you can say that, for all $n in Bbb Z^-$, $n < 0$, and for all $m in Bbb Z^+$, $m > 0$. If there exists an element $k$ in the intersection of the two, this means $k<0$, but also $k>0$, which is simply not possible.






              share|cite|improve this answer









              $endgroup$

















                4












                $begingroup$

                I don't really think there is any particularly "elegant" logic needed - simply that they don't share a common element. It basically amounts to "there is no integer which is both positive and negative."



                I guess if you want to argue it in a somewhat formal way, you can say that, for all $n in Bbb Z^-$, $n < 0$, and for all $m in Bbb Z^+$, $m > 0$. If there exists an element $k$ in the intersection of the two, this means $k<0$, but also $k>0$, which is simply not possible.






                share|cite|improve this answer









                $endgroup$















                  4












                  4








                  4





                  $begingroup$

                  I don't really think there is any particularly "elegant" logic needed - simply that they don't share a common element. It basically amounts to "there is no integer which is both positive and negative."



                  I guess if you want to argue it in a somewhat formal way, you can say that, for all $n in Bbb Z^-$, $n < 0$, and for all $m in Bbb Z^+$, $m > 0$. If there exists an element $k$ in the intersection of the two, this means $k<0$, but also $k>0$, which is simply not possible.






                  share|cite|improve this answer









                  $endgroup$



                  I don't really think there is any particularly "elegant" logic needed - simply that they don't share a common element. It basically amounts to "there is no integer which is both positive and negative."



                  I guess if you want to argue it in a somewhat formal way, you can say that, for all $n in Bbb Z^-$, $n < 0$, and for all $m in Bbb Z^+$, $m > 0$. If there exists an element $k$ in the intersection of the two, this means $k<0$, but also $k>0$, which is simply not possible.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Mar 29 at 3:48









                  Eevee TrainerEevee Trainer

                  9,70031740




                  9,70031740





















                      0












                      $begingroup$

                      An intersection of two sets is the set of elements that are in both sets.



                      $mathbb Z^+$ is the set of integers that are positive and $mathbb Z^-$ is the set of integer that are negative. So $mathbb Z^+ cap mathbb Z^+$ are the set of integers that are both positive and negative.



                      To be negative is to be less than $0$ and to be positive is to be bigger than $0$. A fundamental principal of real numbers is that for any $a,b$ either $a < b; a=b$ or $a > b$-- exactly one and only one of those is true. So an integer being both greater than and less than $0$ is impossible.






                      share|cite|improve this answer









                      $endgroup$

















                        0












                        $begingroup$

                        An intersection of two sets is the set of elements that are in both sets.



                        $mathbb Z^+$ is the set of integers that are positive and $mathbb Z^-$ is the set of integer that are negative. So $mathbb Z^+ cap mathbb Z^+$ are the set of integers that are both positive and negative.



                        To be negative is to be less than $0$ and to be positive is to be bigger than $0$. A fundamental principal of real numbers is that for any $a,b$ either $a < b; a=b$ or $a > b$-- exactly one and only one of those is true. So an integer being both greater than and less than $0$ is impossible.






                        share|cite|improve this answer









                        $endgroup$















                          0












                          0








                          0





                          $begingroup$

                          An intersection of two sets is the set of elements that are in both sets.



                          $mathbb Z^+$ is the set of integers that are positive and $mathbb Z^-$ is the set of integer that are negative. So $mathbb Z^+ cap mathbb Z^+$ are the set of integers that are both positive and negative.



                          To be negative is to be less than $0$ and to be positive is to be bigger than $0$. A fundamental principal of real numbers is that for any $a,b$ either $a < b; a=b$ or $a > b$-- exactly one and only one of those is true. So an integer being both greater than and less than $0$ is impossible.






                          share|cite|improve this answer









                          $endgroup$



                          An intersection of two sets is the set of elements that are in both sets.



                          $mathbb Z^+$ is the set of integers that are positive and $mathbb Z^-$ is the set of integer that are negative. So $mathbb Z^+ cap mathbb Z^+$ are the set of integers that are both positive and negative.



                          To be negative is to be less than $0$ and to be positive is to be bigger than $0$. A fundamental principal of real numbers is that for any $a,b$ either $a < b; a=b$ or $a > b$-- exactly one and only one of those is true. So an integer being both greater than and less than $0$ is impossible.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Mar 30 at 0:48









                          fleabloodfleablood

                          73.8k22891




                          73.8k22891



























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