Prove the boundedness condition











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Suppose $a_ngeq 0.$ Then $sum_{n=1}^{infty}a_n$ converges if and only if the sequence of partial sums $(s_n)=(sum_{j=1}^na_j)$ is bounded. Use the axiom of completeness or one of its consequences to prove this result.



So the axiom of completeness says that there are no 'gaps' in the real number line. But I don't know where to USE the axiom of completeness










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  • $a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
    – m.bazza
    Nov 17 at 21:02








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    The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
    – Saucy O'Path
    Nov 17 at 21:03












  • The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
    – m.bazza
    Nov 17 at 21:05















up vote
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Suppose $a_ngeq 0.$ Then $sum_{n=1}^{infty}a_n$ converges if and only if the sequence of partial sums $(s_n)=(sum_{j=1}^na_j)$ is bounded. Use the axiom of completeness or one of its consequences to prove this result.



So the axiom of completeness says that there are no 'gaps' in the real number line. But I don't know where to USE the axiom of completeness










share|cite|improve this question
























  • $a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
    – m.bazza
    Nov 17 at 21:02








  • 1




    The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
    – Saucy O'Path
    Nov 17 at 21:03












  • The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
    – m.bazza
    Nov 17 at 21:05













up vote
0
down vote

favorite









up vote
0
down vote

favorite











Suppose $a_ngeq 0.$ Then $sum_{n=1}^{infty}a_n$ converges if and only if the sequence of partial sums $(s_n)=(sum_{j=1}^na_j)$ is bounded. Use the axiom of completeness or one of its consequences to prove this result.



So the axiom of completeness says that there are no 'gaps' in the real number line. But I don't know where to USE the axiom of completeness










share|cite|improve this question















Suppose $a_ngeq 0.$ Then $sum_{n=1}^{infty}a_n$ converges if and only if the sequence of partial sums $(s_n)=(sum_{j=1}^na_j)$ is bounded. Use the axiom of completeness or one of its consequences to prove this result.



So the axiom of completeness says that there are no 'gaps' in the real number line. But I don't know where to USE the axiom of completeness







sequences-and-series






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edited Nov 17 at 21:05









John B

12.2k51740




12.2k51740










asked Nov 17 at 20:59









m.bazza

827




827












  • $a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
    – m.bazza
    Nov 17 at 21:02








  • 1




    The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
    – Saucy O'Path
    Nov 17 at 21:03












  • The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
    – m.bazza
    Nov 17 at 21:05


















  • $a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
    – m.bazza
    Nov 17 at 21:02








  • 1




    The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
    – Saucy O'Path
    Nov 17 at 21:03












  • The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
    – m.bazza
    Nov 17 at 21:05
















$a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
– m.bazza
Nov 17 at 21:02






$a_ngeq 0$ as stated in the question <--- a reply to a deleted comment
– m.bazza
Nov 17 at 21:02






1




1




The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
– Saucy O'Path
Nov 17 at 21:03






The first step towards using something is to state it. Not the thing you were told it kind-of means, not the thing you think it means: the actual statement.
– Saucy O'Path
Nov 17 at 21:03














The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
– m.bazza
Nov 17 at 21:05




The axiom is: Every non-empty subset of the reals that is bounded above has a least upper bound.
– m.bazza
Nov 17 at 21:05










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The axiom of completeness implies that a nonempty set of real numbers which is bounded above has a least upper bound.



In your case the sequence of partial sum is nonempty and the supernum happens to be the limit.



You use definition of the least upper bound to prove your statement.






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    up vote
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    down vote













    The axiom of completeness implies that a nonempty set of real numbers which is bounded above has a least upper bound.



    In your case the sequence of partial sum is nonempty and the supernum happens to be the limit.



    You use definition of the least upper bound to prove your statement.






    share|cite|improve this answer

























      up vote
      0
      down vote













      The axiom of completeness implies that a nonempty set of real numbers which is bounded above has a least upper bound.



      In your case the sequence of partial sum is nonempty and the supernum happens to be the limit.



      You use definition of the least upper bound to prove your statement.






      share|cite|improve this answer























        up vote
        0
        down vote










        up vote
        0
        down vote









        The axiom of completeness implies that a nonempty set of real numbers which is bounded above has a least upper bound.



        In your case the sequence of partial sum is nonempty and the supernum happens to be the limit.



        You use definition of the least upper bound to prove your statement.






        share|cite|improve this answer












        The axiom of completeness implies that a nonempty set of real numbers which is bounded above has a least upper bound.



        In your case the sequence of partial sum is nonempty and the supernum happens to be the limit.



        You use definition of the least upper bound to prove your statement.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 17 at 21:07









        Mohammad Riazi-Kermani

        40.3k41958




        40.3k41958






























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