Limit $ lim_{ntoinfty} left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}$
up vote
3
down vote
favorite
I'm required to compute the limit of the following sequence:
$$ lim_{ntoinfty} left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}$$
I'm not sure as to how to approach it. I've tried tackling it in a few ways, but none of them led me to a form I know how to tackle.
Let $a_n$ denote the base.
$$ lim_{ntoinfty}(a_n)^{frac{n^2}{1-n}}= left(lim_{ntoinfty}(a_n)^{large frac{1}{1-n}}right)^{n^2}=lim_{ntoinfty} left(sqrt[1-n]{a_n}right)^{n^2}=1^{infty} $$
From there though I don't know how to compute:
$$e^{lim_{ntoinfty} left(sqrt[n-1]{a_n}n^2right)}$$
I tried using the ln function though I couldn't get any further. I'd be glad for help :)
real-analysis calculus limits
add a comment |
up vote
3
down vote
favorite
I'm required to compute the limit of the following sequence:
$$ lim_{ntoinfty} left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}$$
I'm not sure as to how to approach it. I've tried tackling it in a few ways, but none of them led me to a form I know how to tackle.
Let $a_n$ denote the base.
$$ lim_{ntoinfty}(a_n)^{frac{n^2}{1-n}}= left(lim_{ntoinfty}(a_n)^{large frac{1}{1-n}}right)^{n^2}=lim_{ntoinfty} left(sqrt[1-n]{a_n}right)^{n^2}=1^{infty} $$
From there though I don't know how to compute:
$$e^{lim_{ntoinfty} left(sqrt[n-1]{a_n}n^2right)}$$
I tried using the ln function though I couldn't get any further. I'd be glad for help :)
real-analysis calculus limits
add a comment |
up vote
3
down vote
favorite
up vote
3
down vote
favorite
I'm required to compute the limit of the following sequence:
$$ lim_{ntoinfty} left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}$$
I'm not sure as to how to approach it. I've tried tackling it in a few ways, but none of them led me to a form I know how to tackle.
Let $a_n$ denote the base.
$$ lim_{ntoinfty}(a_n)^{frac{n^2}{1-n}}= left(lim_{ntoinfty}(a_n)^{large frac{1}{1-n}}right)^{n^2}=lim_{ntoinfty} left(sqrt[1-n]{a_n}right)^{n^2}=1^{infty} $$
From there though I don't know how to compute:
$$e^{lim_{ntoinfty} left(sqrt[n-1]{a_n}n^2right)}$$
I tried using the ln function though I couldn't get any further. I'd be glad for help :)
real-analysis calculus limits
I'm required to compute the limit of the following sequence:
$$ lim_{ntoinfty} left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}$$
I'm not sure as to how to approach it. I've tried tackling it in a few ways, but none of them led me to a form I know how to tackle.
Let $a_n$ denote the base.
$$ lim_{ntoinfty}(a_n)^{frac{n^2}{1-n}}= left(lim_{ntoinfty}(a_n)^{large frac{1}{1-n}}right)^{n^2}=lim_{ntoinfty} left(sqrt[1-n]{a_n}right)^{n^2}=1^{infty} $$
From there though I don't know how to compute:
$$e^{lim_{ntoinfty} left(sqrt[n-1]{a_n}n^2right)}$$
I tried using the ln function though I couldn't get any further. I'd be glad for help :)
real-analysis calculus limits
real-analysis calculus limits
edited Dec 5 at 13:26
Arjang
5,56662363
5,56662363
asked Dec 5 at 10:47
Moshe
376
376
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
up vote
4
down vote
accepted
HINT
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}sim ccdot left(frac32right)^{-n}$$
indeed
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac32right)^{-n}left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}$$
and
$$left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left[left(1-frac{frac53n+frac13}{2n^2+n+1}right)^{frac{2n^2+n+1}{frac53n+frac13}}right]^{frac{frac53n^3+frac13n^2}{(2n^2+n+1)(1-n)}}toleft(frac1eright)^{-frac56}$$
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
|
show 2 more comments
up vote
6
down vote
You can estimate:
$$frac{2n^2+n+1}{3n^2-n+1}<frac{3}{4}, n>7;$$
$$0<left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}=left(frac{2n^2+n+1}{3n^2-n+1}right)^{large frac{n^2}{n-1}}<left(frac34right)^{large frac{n^2}{n-1}}=left(frac34right)^{n+1+large frac{1}{n-1}}to 0.$$
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
add a comment |
up vote
0
down vote
You can't reduce this to the limit form of the exponential function, because the limit of the content of the bracket is 3/2. But the exponent becomes more as $-n$ as $ntoinfty$; so you have the the reciprocal of a positive-exponentially increasing number.
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3026929%2flimit-lim-n-to-infty-left-frac3n2-n12n2n1-right-large-fracn%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
4
down vote
accepted
HINT
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}sim ccdot left(frac32right)^{-n}$$
indeed
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac32right)^{-n}left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}$$
and
$$left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left[left(1-frac{frac53n+frac13}{2n^2+n+1}right)^{frac{2n^2+n+1}{frac53n+frac13}}right]^{frac{frac53n^3+frac13n^2}{(2n^2+n+1)(1-n)}}toleft(frac1eright)^{-frac56}$$
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
|
show 2 more comments
up vote
4
down vote
accepted
HINT
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}sim ccdot left(frac32right)^{-n}$$
indeed
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac32right)^{-n}left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}$$
and
$$left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left[left(1-frac{frac53n+frac13}{2n^2+n+1}right)^{frac{2n^2+n+1}{frac53n+frac13}}right]^{frac{frac53n^3+frac13n^2}{(2n^2+n+1)(1-n)}}toleft(frac1eright)^{-frac56}$$
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
|
show 2 more comments
up vote
4
down vote
accepted
up vote
4
down vote
accepted
HINT
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}sim ccdot left(frac32right)^{-n}$$
indeed
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac32right)^{-n}left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}$$
and
$$left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left[left(1-frac{frac53n+frac13}{2n^2+n+1}right)^{frac{2n^2+n+1}{frac53n+frac13}}right]^{frac{frac53n^3+frac13n^2}{(2n^2+n+1)(1-n)}}toleft(frac1eright)^{-frac56}$$
HINT
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}sim ccdot left(frac32right)^{-n}$$
indeed
$$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac32right)^{-n}left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}$$
and
$$left(frac{2n^2-frac23n+frac23}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left[left(1-frac{frac53n+frac13}{2n^2+n+1}right)^{frac{2n^2+n+1}{frac53n+frac13}}right]^{frac{frac53n^3+frac13n^2}{(2n^2+n+1)(1-n)}}toleft(frac1eright)^{-frac56}$$
edited Dec 5 at 15:13
answered Dec 5 at 10:49
gimusi
92.9k94495
92.9k94495
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
|
show 2 more comments
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
I observed that, it leads to 0 but subtituing larger values in the original form gives me other value
– Moshe
Dec 5 at 11:05
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
@Moshe To prove that we can proceed as follows $$left(frac{3n^2-n+1}{2n^2+n+1}right)^{frac{n^2}{1-n}}=left(frac{3n^2}{2n^2}right)^{-frac{n^2}{n-1}}cdot left(frac{1-1/3n+1/3n^2}{1+1/2n+1/2n^2}right)^{-frac{n^2}{n-1}}$$ and the second part on the RHS tends to 1.
– gimusi
Dec 5 at 11:16
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
Nice and simple (as usual !). Cheers.
– Claude Leibovici
Dec 5 at 11:25
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
@ClaudeLeibovici Thanks Claude! Much appreciative from you! Many cheers :)
– gimusi
Dec 5 at 11:28
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
"[T]he second part on the RHS" does not converge to 1 (hence the equivalence sign in the answer is wrong).
– Did
Dec 5 at 15:01
|
show 2 more comments
up vote
6
down vote
You can estimate:
$$frac{2n^2+n+1}{3n^2-n+1}<frac{3}{4}, n>7;$$
$$0<left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}=left(frac{2n^2+n+1}{3n^2-n+1}right)^{large frac{n^2}{n-1}}<left(frac34right)^{large frac{n^2}{n-1}}=left(frac34right)^{n+1+large frac{1}{n-1}}to 0.$$
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
add a comment |
up vote
6
down vote
You can estimate:
$$frac{2n^2+n+1}{3n^2-n+1}<frac{3}{4}, n>7;$$
$$0<left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}=left(frac{2n^2+n+1}{3n^2-n+1}right)^{large frac{n^2}{n-1}}<left(frac34right)^{large frac{n^2}{n-1}}=left(frac34right)^{n+1+large frac{1}{n-1}}to 0.$$
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
add a comment |
up vote
6
down vote
up vote
6
down vote
You can estimate:
$$frac{2n^2+n+1}{3n^2-n+1}<frac{3}{4}, n>7;$$
$$0<left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}=left(frac{2n^2+n+1}{3n^2-n+1}right)^{large frac{n^2}{n-1}}<left(frac34right)^{large frac{n^2}{n-1}}=left(frac34right)^{n+1+large frac{1}{n-1}}to 0.$$
You can estimate:
$$frac{2n^2+n+1}{3n^2-n+1}<frac{3}{4}, n>7;$$
$$0<left(frac{3n^2-n+1}{2n^2+n+1}right)^{large frac{n^2}{1-n}}=left(frac{2n^2+n+1}{3n^2-n+1}right)^{large frac{n^2}{n-1}}<left(frac34right)^{large frac{n^2}{n-1}}=left(frac34right)^{n+1+large frac{1}{n-1}}to 0.$$
answered Dec 5 at 12:15
farruhota
18.7k2736
18.7k2736
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
add a comment |
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
very nice alternative approach (+1).
– gimusi
Dec 5 at 12:58
Thank you gimusi.
– farruhota
Dec 5 at 13:01
Thank you gimusi.
– farruhota
Dec 5 at 13:01
add a comment |
up vote
0
down vote
You can't reduce this to the limit form of the exponential function, because the limit of the content of the bracket is 3/2. But the exponent becomes more as $-n$ as $ntoinfty$; so you have the the reciprocal of a positive-exponentially increasing number.
add a comment |
up vote
0
down vote
You can't reduce this to the limit form of the exponential function, because the limit of the content of the bracket is 3/2. But the exponent becomes more as $-n$ as $ntoinfty$; so you have the the reciprocal of a positive-exponentially increasing number.
add a comment |
up vote
0
down vote
up vote
0
down vote
You can't reduce this to the limit form of the exponential function, because the limit of the content of the bracket is 3/2. But the exponent becomes more as $-n$ as $ntoinfty$; so you have the the reciprocal of a positive-exponentially increasing number.
You can't reduce this to the limit form of the exponential function, because the limit of the content of the bracket is 3/2. But the exponent becomes more as $-n$ as $ntoinfty$; so you have the the reciprocal of a positive-exponentially increasing number.
answered Dec 5 at 14:14
AmbretteOrrisey
54110
54110
add a comment |
add a comment |
Thanks for contributing an answer to Mathematics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3026929%2flimit-lim-n-to-infty-left-frac3n2-n12n2n1-right-large-fracn%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown