How can I find $lim_{nrightarrowinfty}(1+frac{x}n)^{sqrt{n}}$?











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How can I find $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}};?$$




I know $lim_{nrightarrowinfty}left(1+frac{x}nright)^{n} = exp (x)$ but I don't know how can I put the definition in this particular limit.



I know then, that $lim_{nrightarrowinfty}big(1+frac{x}nbig)=1$, but I don't think this is right to consider.










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    up vote
    3
    down vote

    favorite













    How can I find $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}};?$$




    I know $lim_{nrightarrowinfty}left(1+frac{x}nright)^{n} = exp (x)$ but I don't know how can I put the definition in this particular limit.



    I know then, that $lim_{nrightarrowinfty}big(1+frac{x}nbig)=1$, but I don't think this is right to consider.










    share|cite|improve this question


























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite












      How can I find $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}};?$$




      I know $lim_{nrightarrowinfty}left(1+frac{x}nright)^{n} = exp (x)$ but I don't know how can I put the definition in this particular limit.



      I know then, that $lim_{nrightarrowinfty}big(1+frac{x}nbig)=1$, but I don't think this is right to consider.










      share|cite|improve this question
















      How can I find $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}};?$$




      I know $lim_{nrightarrowinfty}left(1+frac{x}nright)^{n} = exp (x)$ but I don't know how can I put the definition in this particular limit.



      I know then, that $lim_{nrightarrowinfty}big(1+frac{x}nbig)=1$, but I don't think this is right to consider.







      real-analysis sequences-and-series limits exponential-function






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      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Nov 20 at 15:22









      amWhy

      191k27223439




      191k27223439










      asked Nov 20 at 14:46









      Dada

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      498






















          5 Answers
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          up vote
          6
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          $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}}$$
          From
          $$lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{nrightarrowinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ **, we get
          $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = e^0=1$$



          EDIT
          I add the note bellow as my calculation was considered insufficiently justified



          **and because the terms are positive, and we don't have an indeterminate case $0^0$ or $1^{infty}$ or $infty ^0,;$






          share|cite|improve this answer



















          • 4




            One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
            – user587192
            Nov 20 at 15:12












          • Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
            – user376343
            Nov 20 at 15:18








          • 1




            What do you use for the "we get..." step in the last line?
            – user587192
            Nov 20 at 15:19






          • 2




            @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
            – Jam
            Nov 20 at 15:26








          • 1




            From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
            – user587192
            Nov 20 at 15:44




















          up vote
          5
          down vote













          Hint:



          Compute the limit of the log: $;sqrt nlogBigl(1+ dfrac xnBigr)$ and use equivalence:
          $$log(1+u)sim_0 u.$$






          share|cite|improve this answer























          • I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
            – Jam
            Nov 20 at 15:32






          • 1




            Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
            – Shalop
            Nov 20 at 16:25






          • 1




            @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
            – Bernard
            Nov 20 at 16:53










          • That wasn’t my comment though. It was jam
            – Shalop
            Nov 20 at 19:00


















          up vote
          4
          down vote













          Let $y=(1+frac{x}{n})^{sqrt{n}}$. Note that
          $$
          ln y=sqrt{n}ln(1+frac{x}{n})=frac{ln(1+frac{x}{n})}{1/sqrt{n}}.
          $$

          As $ntoinfty$, this is a limit of the form $0/0$. Thus, we may apply L'Hopital's rule to obtain that
          $$
          lim_{ntoinfty}ln y=lim_{ntoinfty}frac{-frac{x}{n^{2}}/(1+frac{x}{n})}{-frac{1}{2}n^{-3/2}}=lim_{ntoinfty}frac{2x}{sqrt{n}+frac{x}{sqrt{n}}}=0
          $$

          Thus,
          $$
          lim_{ntoinfty}y=lim_{ntoinfty}e^{ln(y)}=e^{left(lim_{ntoinfty}ln(y)right)}=e^{0}=1.
          $$






          share|cite|improve this answer




























            up vote
            3
            down vote













            Hint for $xgeq1$:




            1. The expression and therefore the limit is relatively easily seen to be greater than or equal to $1$

            2. The expression is for any $epsilon>0$ eventually smaller than $left(1+frac xnright)^{epsilon n}$






            share|cite|improve this answer























            • Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
              – Jam
              Nov 20 at 15:09










            • @Jam You're right. I've modified my hint.
              – Arthur
              Nov 20 at 15:12


















            up vote
            2
            down vote













            By L'Hopital,
            $$
            lim_{ytoinfty}sqrt{y}log(1+frac{x}{y})
            =lim_{tto 0}frac{log(1+tx)}{sqrt{t}}
            =lim_{tto 0}dfrac{frac{x}{1+tx}}{frac{1}{2sqrt{t}}}=0.
            $$

            Now one can use the continuity of the exponential function:
            $$
            lim_{ntoinfty}expleft[sqrt{n}log(1+frac{x}{n})right]
            =expleft[lim_{ntoinfty}sqrt{n}log(1+frac{x}{n})right]=1.
            $$






            share|cite|improve this answer





















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              up vote
              6
              down vote













              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}}$$
              From
              $$lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{nrightarrowinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ **, we get
              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = e^0=1$$



              EDIT
              I add the note bellow as my calculation was considered insufficiently justified



              **and because the terms are positive, and we don't have an indeterminate case $0^0$ or $1^{infty}$ or $infty ^0,;$






              share|cite|improve this answer



















              • 4




                One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
                – user587192
                Nov 20 at 15:12












              • Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
                – user376343
                Nov 20 at 15:18








              • 1




                What do you use for the "we get..." step in the last line?
                – user587192
                Nov 20 at 15:19






              • 2




                @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
                – Jam
                Nov 20 at 15:26








              • 1




                From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
                – user587192
                Nov 20 at 15:44

















              up vote
              6
              down vote













              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}}$$
              From
              $$lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{nrightarrowinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ **, we get
              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = e^0=1$$



              EDIT
              I add the note bellow as my calculation was considered insufficiently justified



              **and because the terms are positive, and we don't have an indeterminate case $0^0$ or $1^{infty}$ or $infty ^0,;$






              share|cite|improve this answer



















              • 4




                One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
                – user587192
                Nov 20 at 15:12












              • Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
                – user376343
                Nov 20 at 15:18








              • 1




                What do you use for the "we get..." step in the last line?
                – user587192
                Nov 20 at 15:19






              • 2




                @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
                – Jam
                Nov 20 at 15:26








              • 1




                From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
                – user587192
                Nov 20 at 15:44















              up vote
              6
              down vote










              up vote
              6
              down vote









              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}}$$
              From
              $$lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{nrightarrowinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ **, we get
              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = e^0=1$$



              EDIT
              I add the note bellow as my calculation was considered insufficiently justified



              **and because the terms are positive, and we don't have an indeterminate case $0^0$ or $1^{infty}$ or $infty ^0,;$






              share|cite|improve this answer














              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}}$$
              From
              $$lim_{nrightarrowinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{nrightarrowinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ **, we get
              $$lim_{nrightarrowinfty}left(1+frac{x}nright)^{sqrt{n}} = e^0=1$$



              EDIT
              I add the note bellow as my calculation was considered insufficiently justified



              **and because the terms are positive, and we don't have an indeterminate case $0^0$ or $1^{infty}$ or $infty ^0,;$







              share|cite|improve this answer














              share|cite|improve this answer



              share|cite|improve this answer








              edited Nov 20 at 18:55

























              answered Nov 20 at 15:03









              user376343

              2,5081718




              2,5081718








              • 4




                One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
                – user587192
                Nov 20 at 15:12












              • Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
                – user376343
                Nov 20 at 15:18








              • 1




                What do you use for the "we get..." step in the last line?
                – user587192
                Nov 20 at 15:19






              • 2




                @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
                – Jam
                Nov 20 at 15:26








              • 1




                From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
                – user587192
                Nov 20 at 15:44
















              • 4




                One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
                – user587192
                Nov 20 at 15:12












              • Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
                – user376343
                Nov 20 at 15:18








              • 1




                What do you use for the "we get..." step in the last line?
                – user587192
                Nov 20 at 15:19






              • 2




                @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
                – Jam
                Nov 20 at 15:26








              • 1




                From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
                – user587192
                Nov 20 at 15:44










              4




              4




              One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
              – user587192
              Nov 20 at 15:12






              One needs an argument for "if $a_nto a$ and $b_nto b$ ($b_n,bgeqslant0, a_n,a>0$) then $a_n^{b_n}to a^b$".
              – user587192
              Nov 20 at 15:12














              Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
              – user376343
              Nov 20 at 15:18






              Or, if you prefer, put $t={n over x}.$ The mentioned limit becomes $lim_{t to infty} (1+{1over t})^{t}.$
              – user376343
              Nov 20 at 15:18






              1




              1




              What do you use for the "we get..." step in the last line?
              – user587192
              Nov 20 at 15:19




              What do you use for the "we get..." step in the last line?
              – user587192
              Nov 20 at 15:19




              2




              2




              @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
              – Jam
              Nov 20 at 15:26






              @user376343 I think what user587 is driving at is that you've assumed that you can distribute the limit $lim_n a_n^{b_n} $ into $(lim_n a_n)^{(lim_n b_n)}$ but this isn't necessarily justified.
              – Jam
              Nov 20 at 15:26






              1




              1




              From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
              – user587192
              Nov 20 at 15:44






              From $$lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]=e quad text{and} quad lim_{ntoinfty}{{frac{x}{n}}{sqrt{n}}}=0,$$ we get $$lim_{ntoinfty}left(1+frac{x}nright)^{sqrt{n}} =lim_{ntoinfty}left[left(1+frac{x}nright)^{{frac{n}{x}}}right]^{{frac{x}{n}}{sqrt{n}}} color{red}{ =left[lim_{ntoinfty}left(1+frac{x}nright)^{{frac{n}{x}}}right]^{lim_{ntoinfty}{frac{x}{n}}{sqrt{n}}} } color{blue}{= e^0} $$ You have the blue one, but you need the red part, which is not explicitly justified.
              – user587192
              Nov 20 at 15:44












              up vote
              5
              down vote













              Hint:



              Compute the limit of the log: $;sqrt nlogBigl(1+ dfrac xnBigr)$ and use equivalence:
              $$log(1+u)sim_0 u.$$






              share|cite|improve this answer























              • I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
                – Jam
                Nov 20 at 15:32






              • 1




                Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
                – Shalop
                Nov 20 at 16:25






              • 1




                @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
                – Bernard
                Nov 20 at 16:53










              • That wasn’t my comment though. It was jam
                – Shalop
                Nov 20 at 19:00















              up vote
              5
              down vote













              Hint:



              Compute the limit of the log: $;sqrt nlogBigl(1+ dfrac xnBigr)$ and use equivalence:
              $$log(1+u)sim_0 u.$$






              share|cite|improve this answer























              • I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
                – Jam
                Nov 20 at 15:32






              • 1




                Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
                – Shalop
                Nov 20 at 16:25






              • 1




                @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
                – Bernard
                Nov 20 at 16:53










              • That wasn’t my comment though. It was jam
                – Shalop
                Nov 20 at 19:00













              up vote
              5
              down vote










              up vote
              5
              down vote









              Hint:



              Compute the limit of the log: $;sqrt nlogBigl(1+ dfrac xnBigr)$ and use equivalence:
              $$log(1+u)sim_0 u.$$






              share|cite|improve this answer














              Hint:



              Compute the limit of the log: $;sqrt nlogBigl(1+ dfrac xnBigr)$ and use equivalence:
              $$log(1+u)sim_0 u.$$







              share|cite|improve this answer














              share|cite|improve this answer



              share|cite|improve this answer








              edited Nov 20 at 16:49

























              answered Nov 20 at 14:52









              Bernard

              116k637108




              116k637108












              • I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
                – Jam
                Nov 20 at 15:32






              • 1




                Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
                – Shalop
                Nov 20 at 16:25






              • 1




                @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
                – Bernard
                Nov 20 at 16:53










              • That wasn’t my comment though. It was jam
                – Shalop
                Nov 20 at 19:00


















              • I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
                – Jam
                Nov 20 at 15:32






              • 1




                Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
                – Shalop
                Nov 20 at 16:25






              • 1




                @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
                – Bernard
                Nov 20 at 16:53










              • That wasn’t my comment though. It was jam
                – Shalop
                Nov 20 at 19:00
















              I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
              – Jam
              Nov 20 at 15:32




              I'd like to add an addendum to this answer since I wasn't sure about justifying the exchange of $log(1+u)$ with $u$. Since $log(1+u)sim u$, $lim_{utoinfty}frac{log(1+u)}{u}=1$ so $lim_{ntoinfty}frac{log(1+x/n)/left(frac{x}{n}right)}{sqrt{n}/{left(frac{x}{n}right)}}=frac{lim(ldots)}{lim_{ntoinfty}sqrt{n}{left(frac{n}{x}right)}}$.
              – Jam
              Nov 20 at 15:32




              1




              1




              Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
              – Shalop
              Nov 20 at 16:25




              Should just be $sqrt n$ our front of the log, not $1/sqrt n$.
              – Shalop
              Nov 20 at 16:25




              1




              1




              @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
              – Bernard
              Nov 20 at 16:53




              @Shalop: Thanks for pointing the typo. I've fixed it. For your first comment, I don't think it's necessary: I specified I used equivalence, in the sense of asymptotic analysis, and use the rules thereof (compatibility with product and quotient).
              – Bernard
              Nov 20 at 16:53












              That wasn’t my comment though. It was jam
              – Shalop
              Nov 20 at 19:00




              That wasn’t my comment though. It was jam
              – Shalop
              Nov 20 at 19:00










              up vote
              4
              down vote













              Let $y=(1+frac{x}{n})^{sqrt{n}}$. Note that
              $$
              ln y=sqrt{n}ln(1+frac{x}{n})=frac{ln(1+frac{x}{n})}{1/sqrt{n}}.
              $$

              As $ntoinfty$, this is a limit of the form $0/0$. Thus, we may apply L'Hopital's rule to obtain that
              $$
              lim_{ntoinfty}ln y=lim_{ntoinfty}frac{-frac{x}{n^{2}}/(1+frac{x}{n})}{-frac{1}{2}n^{-3/2}}=lim_{ntoinfty}frac{2x}{sqrt{n}+frac{x}{sqrt{n}}}=0
              $$

              Thus,
              $$
              lim_{ntoinfty}y=lim_{ntoinfty}e^{ln(y)}=e^{left(lim_{ntoinfty}ln(y)right)}=e^{0}=1.
              $$






              share|cite|improve this answer

























                up vote
                4
                down vote













                Let $y=(1+frac{x}{n})^{sqrt{n}}$. Note that
                $$
                ln y=sqrt{n}ln(1+frac{x}{n})=frac{ln(1+frac{x}{n})}{1/sqrt{n}}.
                $$

                As $ntoinfty$, this is a limit of the form $0/0$. Thus, we may apply L'Hopital's rule to obtain that
                $$
                lim_{ntoinfty}ln y=lim_{ntoinfty}frac{-frac{x}{n^{2}}/(1+frac{x}{n})}{-frac{1}{2}n^{-3/2}}=lim_{ntoinfty}frac{2x}{sqrt{n}+frac{x}{sqrt{n}}}=0
                $$

                Thus,
                $$
                lim_{ntoinfty}y=lim_{ntoinfty}e^{ln(y)}=e^{left(lim_{ntoinfty}ln(y)right)}=e^{0}=1.
                $$






                share|cite|improve this answer























                  up vote
                  4
                  down vote










                  up vote
                  4
                  down vote









                  Let $y=(1+frac{x}{n})^{sqrt{n}}$. Note that
                  $$
                  ln y=sqrt{n}ln(1+frac{x}{n})=frac{ln(1+frac{x}{n})}{1/sqrt{n}}.
                  $$

                  As $ntoinfty$, this is a limit of the form $0/0$. Thus, we may apply L'Hopital's rule to obtain that
                  $$
                  lim_{ntoinfty}ln y=lim_{ntoinfty}frac{-frac{x}{n^{2}}/(1+frac{x}{n})}{-frac{1}{2}n^{-3/2}}=lim_{ntoinfty}frac{2x}{sqrt{n}+frac{x}{sqrt{n}}}=0
                  $$

                  Thus,
                  $$
                  lim_{ntoinfty}y=lim_{ntoinfty}e^{ln(y)}=e^{left(lim_{ntoinfty}ln(y)right)}=e^{0}=1.
                  $$






                  share|cite|improve this answer












                  Let $y=(1+frac{x}{n})^{sqrt{n}}$. Note that
                  $$
                  ln y=sqrt{n}ln(1+frac{x}{n})=frac{ln(1+frac{x}{n})}{1/sqrt{n}}.
                  $$

                  As $ntoinfty$, this is a limit of the form $0/0$. Thus, we may apply L'Hopital's rule to obtain that
                  $$
                  lim_{ntoinfty}ln y=lim_{ntoinfty}frac{-frac{x}{n^{2}}/(1+frac{x}{n})}{-frac{1}{2}n^{-3/2}}=lim_{ntoinfty}frac{2x}{sqrt{n}+frac{x}{sqrt{n}}}=0
                  $$

                  Thus,
                  $$
                  lim_{ntoinfty}y=lim_{ntoinfty}e^{ln(y)}=e^{left(lim_{ntoinfty}ln(y)right)}=e^{0}=1.
                  $$







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Nov 20 at 15:04









                  ervx

                  10.3k31338




                  10.3k31338






















                      up vote
                      3
                      down vote













                      Hint for $xgeq1$:




                      1. The expression and therefore the limit is relatively easily seen to be greater than or equal to $1$

                      2. The expression is for any $epsilon>0$ eventually smaller than $left(1+frac xnright)^{epsilon n}$






                      share|cite|improve this answer























                      • Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                        – Jam
                        Nov 20 at 15:09










                      • @Jam You're right. I've modified my hint.
                        – Arthur
                        Nov 20 at 15:12















                      up vote
                      3
                      down vote













                      Hint for $xgeq1$:




                      1. The expression and therefore the limit is relatively easily seen to be greater than or equal to $1$

                      2. The expression is for any $epsilon>0$ eventually smaller than $left(1+frac xnright)^{epsilon n}$






                      share|cite|improve this answer























                      • Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                        – Jam
                        Nov 20 at 15:09










                      • @Jam You're right. I've modified my hint.
                        – Arthur
                        Nov 20 at 15:12













                      up vote
                      3
                      down vote










                      up vote
                      3
                      down vote









                      Hint for $xgeq1$:




                      1. The expression and therefore the limit is relatively easily seen to be greater than or equal to $1$

                      2. The expression is for any $epsilon>0$ eventually smaller than $left(1+frac xnright)^{epsilon n}$






                      share|cite|improve this answer














                      Hint for $xgeq1$:




                      1. The expression and therefore the limit is relatively easily seen to be greater than or equal to $1$

                      2. The expression is for any $epsilon>0$ eventually smaller than $left(1+frac xnright)^{epsilon n}$







                      share|cite|improve this answer














                      share|cite|improve this answer



                      share|cite|improve this answer








                      edited Nov 20 at 15:12

























                      answered Nov 20 at 14:52









                      Arthur

                      109k7103186




                      109k7103186












                      • Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                        – Jam
                        Nov 20 at 15:09










                      • @Jam You're right. I've modified my hint.
                        – Arthur
                        Nov 20 at 15:12


















                      • Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                        – Jam
                        Nov 20 at 15:09










                      • @Jam You're right. I've modified my hint.
                        – Arthur
                        Nov 20 at 15:12
















                      Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                      – Jam
                      Nov 20 at 15:09




                      Point 1. is only true for $x>0$. When $x<0$, the expression approaches $1$ from below so I think this argument might need a slight modification
                      – Jam
                      Nov 20 at 15:09












                      @Jam You're right. I've modified my hint.
                      – Arthur
                      Nov 20 at 15:12




                      @Jam You're right. I've modified my hint.
                      – Arthur
                      Nov 20 at 15:12










                      up vote
                      2
                      down vote













                      By L'Hopital,
                      $$
                      lim_{ytoinfty}sqrt{y}log(1+frac{x}{y})
                      =lim_{tto 0}frac{log(1+tx)}{sqrt{t}}
                      =lim_{tto 0}dfrac{frac{x}{1+tx}}{frac{1}{2sqrt{t}}}=0.
                      $$

                      Now one can use the continuity of the exponential function:
                      $$
                      lim_{ntoinfty}expleft[sqrt{n}log(1+frac{x}{n})right]
                      =expleft[lim_{ntoinfty}sqrt{n}log(1+frac{x}{n})right]=1.
                      $$






                      share|cite|improve this answer

























                        up vote
                        2
                        down vote













                        By L'Hopital,
                        $$
                        lim_{ytoinfty}sqrt{y}log(1+frac{x}{y})
                        =lim_{tto 0}frac{log(1+tx)}{sqrt{t}}
                        =lim_{tto 0}dfrac{frac{x}{1+tx}}{frac{1}{2sqrt{t}}}=0.
                        $$

                        Now one can use the continuity of the exponential function:
                        $$
                        lim_{ntoinfty}expleft[sqrt{n}log(1+frac{x}{n})right]
                        =expleft[lim_{ntoinfty}sqrt{n}log(1+frac{x}{n})right]=1.
                        $$






                        share|cite|improve this answer























                          up vote
                          2
                          down vote










                          up vote
                          2
                          down vote









                          By L'Hopital,
                          $$
                          lim_{ytoinfty}sqrt{y}log(1+frac{x}{y})
                          =lim_{tto 0}frac{log(1+tx)}{sqrt{t}}
                          =lim_{tto 0}dfrac{frac{x}{1+tx}}{frac{1}{2sqrt{t}}}=0.
                          $$

                          Now one can use the continuity of the exponential function:
                          $$
                          lim_{ntoinfty}expleft[sqrt{n}log(1+frac{x}{n})right]
                          =expleft[lim_{ntoinfty}sqrt{n}log(1+frac{x}{n})right]=1.
                          $$






                          share|cite|improve this answer












                          By L'Hopital,
                          $$
                          lim_{ytoinfty}sqrt{y}log(1+frac{x}{y})
                          =lim_{tto 0}frac{log(1+tx)}{sqrt{t}}
                          =lim_{tto 0}dfrac{frac{x}{1+tx}}{frac{1}{2sqrt{t}}}=0.
                          $$

                          Now one can use the continuity of the exponential function:
                          $$
                          lim_{ntoinfty}expleft[sqrt{n}log(1+frac{x}{n})right]
                          =expleft[lim_{ntoinfty}sqrt{n}log(1+frac{x}{n})right]=1.
                          $$







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered Nov 20 at 15:11









                          user587192

                          1,295111




                          1,295111






























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