Casually doing math while holding a thermal detonator.
@warlockgnome10155 жыл бұрын
I'm so glad I wasn't the only person thinking this
@prateekbhurkay9376 Жыл бұрын
If he stops doing math, the thermal detonator goes off. It's like the movie Speed.
@lswcs4 жыл бұрын
The "please pause the video and first try for yourself" is always so motivating :) I was lying in my bed and this motivated me to get up and try it :)
@samueljehanno Жыл бұрын
Nice
@AlRoderick7 жыл бұрын
It's clever for you to use the blue pen for "I did this in a different video" because it makes me think your whiteboard has hyperlinks. When I go watch that video and come back will that part turn purple?
@blackpenredpen7 жыл бұрын
Alexander Roderick lol!!! Nice one
@zabrakhan51787 жыл бұрын
+blackpenredpen Hello! Can you make a video on how to solve the integral of this (5x^(2)-x+47)/(x^(3)-x^(2)+16x-16)? But can you do partial fractions with the imaginary roots?
@JayJay-ej6dq6 жыл бұрын
blackpenredpenbluepen
@moregirl45856 жыл бұрын
but there's no hyperlink on the video xd
@munendersingh56316 жыл бұрын
Below
@altacc78363 жыл бұрын
It helps when you keep in mind that the arithmetic rules for limits of sequences only apply if all sequences used actually converge :)
@timtimtimmaah6 жыл бұрын
That it's negative this makes sense considering that limit definition of e approaches e from the left of e.
@fxyang19895 жыл бұрын
Good thinking. It starts from 2 when N=1 and e>2.
@justarandomcatwithmoustache5 жыл бұрын
Isn't it obvious ?
@gljames243 жыл бұрын
It makes sense as the part -ne is starting at e, while the part n(1+1÷n)ⁿ has to reach e as it approaches ∞, so it is starting later.
@masongatz28107 жыл бұрын
Weird things can happen with infinity. This was one of my favorite videos so far!
@FernandoRodriguez-et7qj5 жыл бұрын
Who are you mason? You look like a professor
@General12th3 жыл бұрын
@@FernandoRodriguez-et7qj You are YOU, Fernando? You look like a professor too.
@krukowstudios36865 жыл бұрын
I’d say 0. “en” means “one” in Danish, so it is 1 - 1.
@yuklungleung6205 жыл бұрын
Krukow Studios i would say you are on9
@2ndtik4 жыл бұрын
@@yuklungleung620 saupei la sohai
@modemanslutning Жыл бұрын
For the "intuitive" explanation: The 2nd part, x*e, is like a typical linear function: y=k*x, with the constant being "e". This of course grows linearly. The 1st part, x*(1+1/x)^x, will eventually reach a similar value, the latter part eventually becoming "e", so this term will also become a linear equation essentially, x*e. But it takes a while for it to grow and get closer to the value that is "e". Thus x*(1+1/x)^x is "lagging behind" the other function. After a while it will stabilize though when becoming more linear. The difference between the two functions caused by that lag will thus be e/2 (the minus sign in the limit depends on which of the functions we put first). If you want to see this yourself, plot the two graphs: y(x) = x*e g(x) = x*(1+1/x)^x And measure the height difference for some relatively high value of x. Should be about e/2 = 1.36.
@jordank195 Жыл бұрын
Ah I see the KZbin gods also presented you with a 5yr old video 😂
@leandroteles7857 Жыл бұрын
You can also think of it as a product of 2 functions: One part is the product of x by the constant function "e". The other part is the product of x by the function (1+1/x)^x. This function is NOT constant, and in fact, it only reaches "e" at infinity. Therefore, it is always smaller than the constant function "e".
@FlyNavy9066 жыл бұрын
I was having a crisis thinking Q1 might not be 0 somehow lol
@paul_w5 жыл бұрын
Using ln(1+1/n)=1/n-1/2n²+o(1/n²) and e^(1/n)=1+1/n+o(1/n) you can solve that easily and quickly without using l'hôpital rule and without these weird derivatives. Taylor series are so useful to find limits... You make this looks really hard when it really isn't.
@ramez27757 жыл бұрын
One of the best math channels out there - deserves more subscribers! Keep up the good work!
@PackSciences7 жыл бұрын
That moment when you forget a minus sign
@blackpenredpen7 жыл бұрын
PackSciences so true...
@tollboothjason7 жыл бұрын
That was some fast writing at 6:44 and 6:48! 😁
@FernandoRodriguez-et7qj5 жыл бұрын
toll_booth that wasn’t funny
@FernandoRodriguez-et7qj5 жыл бұрын
You made me rewind the video
@hugolaurent26435 жыл бұрын
You can also use the Taylor expansion twice, with ln (because (1+1/n)^n = e^nln(1+1/n)) And again with exp (you factorizes by ne : ne*(e^-1/2n - 1) and the Taylor expansion of exp(-1/2n) gives us 1-1/2n so finally ne*(-1/2n) which is equal to - e/2 I find this quicker ;)
@Aditya_196 Жыл бұрын
🙂 can u tell me what's Taylor expansion and how did u use it here ?
@gillrowley3 жыл бұрын
Stop blowing my mind!! Actually, keep going. Fascinating videos that bring back some knowledge I haven't used in a long time.
@dugong3696 жыл бұрын
In the process of looking more into your video about generating x and y such that x^y=y^x, I found that (1+1/x)^x and (1+1/x)^(x+1) generates such a pair (directly derived from your method using t). Since these pairs always bracket e, and are almost equidistant from e when they are close to e, a better estimate for e is (1+1/n)^(n+1/2). If you substitute this better estimate for e in your expression and then factor out (1+1/n)^n (and call that e like you did in this video) and then find the limit of the remaining factor, also using the fact that for large n, sqrt(n(n+1)) is about n + 1/2, that limit is quickly found to be -1/2, giving the correct answer -e/2 (not by such a rigorous process, but you might be able to justify it better than I could). No LH rule or derivatives involved, just algebra. Edit: I went through the LH rule procedure for the limit of ((1+1/x)^(x+1/2)*x - e*x) and unless I made an algebra error, this limit is 0. The polynomials in numerator and denominator are one degree higher, but the numerator still cancels out to 1. [Just checked it on Wolfram Alpha, the limit is 0.]
@FuhrerShattercore7 жыл бұрын
The answer makes perfect sense since that would be the accumulation of errors between the limit and the value e. I expected it on the value becoming negative but arriving on exactly -e/2 was pretty amazing
@General12th7 жыл бұрын
I love this channel! It's like the BPRP of KZbin!
@xavierplatiau46355 жыл бұрын
Believe it or not, I did it in my head, using limited developments of ln(1+x) as x goes to 0 and of exp(x). Did it like (1+1/n)^n - e = exp(n ln(1+1/n) ) - e ~ exp(n(1/n - 1/2n^2)) - e = exp(1 - 1/2n) - e = e(exp(-1/2n) - 1) ~ -e/2n And then multiplied by n it leads to -e/2.
@deinauge78944 жыл бұрын
same :) at least very similar to what i thought while preparing a meal... ln(1+1/n) ~1 + n^-1 - 1/2n^-2 ln(first term) - ln(second term) ~(2n)^-1 and with the derivative of ln at en: ln'(en)=(en)^-1 the limit is ((2n)^-1)/((en)^-1) = e/2 higher orders in the expansion of ln vanish obviously ^^
@Aditya_196 Жыл бұрын
😅 can u explain it ?
@restcure7 жыл бұрын
Yesterday the beard ... today the plaid flannel shirt ... tomorrow - full lumberjack? edit: re-watching after three weeks (forgot method - whoops) I felt the desire to add: time to remember it was "x", not "n": about 27 seconds - been there!
@blackpenredpen7 жыл бұрын
restcure maybe!
@veradrix6 жыл бұрын
But he can only apply L'H to function fractions, and functions are in terms of x not n, so he did it right!
@ianmoseley99106 жыл бұрын
Would still have worked if he used d/dn - nothing sacrosanct about using x.
@ianmoseley99106 жыл бұрын
Irina Alexandra functions can use any letter as a variable - if you run out of. letters there are other alphabets
@racheline_nya5 жыл бұрын
@@veradrix it works with any symbol instead of x. you just need to replace every instance of x with that symbol, including the one in d/dx. so d/dn(f(n))=d/dt(f(t))=d/dx(f(x)).
@m.guypirate69002 жыл бұрын
Loved this video! Made me think. I immediately went into desmos and plugged in all of the functions and discovered the -e/2, thought about it, then came back to finish the video.
@ryanchatterjee7 жыл бұрын
This guy's living the dream: beautiful wife, genius son, wears stylish clothes, makes math videos for a living.
@vvalph94836 жыл бұрын
70% of the time i was looking at his beard
@calyodelphi1247 жыл бұрын
I like that you post your mistakes as bloopers either at the beginning or end of the video. It shows us that even the great blackpenredpen is still ultimately human and makes mistakes like the rest of us! :D
@fredsharp74193 жыл бұрын
Brilliant! Your enthusiasm is infectious!
@matchedimpedance6 жыл бұрын
Another approach is to do the binomial expansion of (1+1/n)^n and then subtract the series expansion of e. Multiply the difference by n and the answer falls out. No l’hopitals needed.
@matthewzuelke67217 жыл бұрын
4:30am. Good morning, time for BlackpenRedpen
@blackpenredpen7 жыл бұрын
Matthew Zuelke WOW!!!!!
@tiboletibetain57304 жыл бұрын
Without using complicate tricks: n(1+1/n)^n = n exp(n(1/n -1/2n^2 +o(1/n^2))=nexp(1-1/2n+o(1/n))=ne(1-1/2n+o(1/n))=ne-e/2+o(1) So the limit -e/2 is straightforward
@haydenkarkainen11677 жыл бұрын
Nice video, cool limit I'll try to remember to be careful when n is doing "multiple tasks" in my limit. I feel like it's a really easy thing to misunderstand or accidentally interpret incorrectly.
@JustSimplySilly7 жыл бұрын
You make limits interesting!
@Anas-nu7io7 жыл бұрын
Hi BPRP, can you do a video on the integral of cos(x).sqrt(1-cos(x))? Thanks and I love your videos by the way!
@physicsphysics19565 жыл бұрын
The integral is likely non-elementary.
@reeeeeplease11782 жыл бұрын
Kinda late to the party, try u=1-cos(x) and the integral *should* turn into 1/sqrt(2) * sqrt(1-u) du The rest is quite simple
@evgeniyevgeniy83526 жыл бұрын
You are not right on 4:20 It does matter, becuase "n" is natural and "x" is real. You can't just replace first by second. For example, sin(2*Pi*n) converges to 0, when n=+infinity, but sin(2*Pi*x) diverges when x=+infinity. Would be interesting to watch video, where you explain, when we can do such substitutions, and when we can't.
@blackpenredpen6 жыл бұрын
Evgeniy Baton Ahhh, yes your were right. What I said at 4:20 was bad. But I think the work is still legit. The theorem is: if you have a function such that f(n)=a_n, then we will have if limit of f(x) goes to L as x goes to inf, then a_n goes to L as well. But the converse isn't true, just like your example. So, when I checked the limit as x goes to inf and I got the answer, then I was okay for me to conclude that a_n goes to the same limit. I will make a video on this. Thanks.
@blackpenredpen6 жыл бұрын
Video coming soon! : )
@nath3x Жыл бұрын
THANK YOU SO MUCH!!!!! I das hours on a similar question...all because a little mistake I didnt notice myself. Thank for the video
@mr.soundguy9683 жыл бұрын
This actually gives information about the convergence rate of (1+1/x)^x to e
@jinanlife5 жыл бұрын
the lady at the beginning is absolutely gorgeous
@lucasscoz60903 жыл бұрын
math?
@Myuri31467 жыл бұрын
let's solve this question with very unnecessary complicated, set a complex function f(z)=(1+1/z)^z. now we have f(n)n-en for n to infinity and Im(n)=0, we can calculate Laurent series of f(z)(i won't write here the calculations) to get f(z)=e-e/(2z)+o(1/z^2) hence Lim f(n)n-en=(e-e/(2n)+o(1/n^2))n-en=ne-e/2+o(1/n)-en=-e/2+o(1/n)=-e/2
@danielbenyair3006 жыл бұрын
3:03 it's called desamol or desimait.. (i am not sure) you can find it serching for "the opposite of infinity"
@douglasmagowan49187 жыл бұрын
I posted this comment at flammable maths as well. This was pretty easy if you do a binomial expansion on (1+1/x)^x = 1 + 1 + (1/2!)(1-1/x) + 1/3!(1-1/x)(1-2/x) .... 1/x!(1-1/x)...(1-(x-1)/x) subtract e = 1 + 1 + 1/2! + 1/3! ... multiply through by x. This will leave a collection of constant terms and a collection of 1/x^n terms. You can disregard the 1/x^n terms as they go away as x get to be large. Summing the constant terms you get -1/2(1+1+1/2! + 1/3! ...) = -1/2 e.
@mihaiciorobitca52877 жыл бұрын
You and Peyam are the best
@SJ-ry6br5 жыл бұрын
yes of course! Limit calculation form of 0×∞ should be treated carefully!
@thinhtran35936 жыл бұрын
I wish we had math like this at school instead of boring lectures
@someperson1886 жыл бұрын
The comment @4:10 is some what misleading. If limit as (real) x-> ∞ of F(x) = L, then limit as (integer) n -> ∞ of F(n) = L. However, limit as (real) x-> ∞ of F(x) may not exist but limit as (integer) n -> ∞ of F(n) may exist. Example: F(x) = sin(pi*x)
@BabyXGlitz7 жыл бұрын
or through a numerical approach you can put n as equal to 1.0E9 (or preferably more) and you get the answer as -1.35904 ~ - e/2
@mrflibble57177 жыл бұрын
Keep up the good work, enjoy your Channel!
@qbert86957 жыл бұрын
Nice limit. I've got the same result using Taylor's formula.
@indrada-rf2vu6 жыл бұрын
In Dev I got the same result using a calculator
@Mayank-mf7xr6 жыл бұрын
the lovely doraemon sequence . love you man
@royler88486 жыл бұрын
your addicted to L'h rule like seriously your using it in every lim video
@forcelifeforce5 жыл бұрын
* you're -- It's for "you are."
@mtaur41134 жыл бұрын
ooh, a rare outtake. I totally never have moments like that.
@xiang-yue-fung3 жыл бұрын
"為什麼這個是,欸" lmao I know you can speek chinese but have not evidence of it enough, and this video just bring me laugh. I like your video, and hope you can make more and bring us fun.
@georgepapamichael5907 жыл бұрын
You can also take the logarithm of the expression to begin with. That will make the derivative simpler.
@levkrainov5 жыл бұрын
Another way you could do it is take (1 + 1/n) = e^(1/n) - 1/(2n^2) + O(1/n^3) and go from there.
@duranchen32227 жыл бұрын
the last 4 steps can be simplified if u replace ln(1+ 1/x)with 1/x. 1/x-1/1+x can be cancelled by the denominator 1/x².
@forcelifeforce5 жыл бұрын
That would be 1/x - 1/(1 + x).
@Czeckie6 жыл бұрын
great example on being careful with limits! where is this from? I want more!
@anshumanyadav248165 жыл бұрын
Best video ever made by you 😛💕
@profesordanielalvarez34986 жыл бұрын
This limit is a curious example of the subtlety with which one works with the infinite potential and the actual infinity.
@barryzeeberg36722 жыл бұрын
2:44 can you really say that the limit is "e - e", since the limit operator does not distribute over the individual terms unless each component converges, but "n" itself goes to infinity so we cannot say that converges?
@AayushSrivastava03072 жыл бұрын
Another easy method using taylors theorem,let x=1/n so limit becomes lim x tends to 0 of ((1+x)^(1/x)-e)/x now use Taylor exapnsion of (1+x)^1/x which is e(1-x/2+11x^2/24+O(x^3)) and solve it very easily to get -e/2
@frenchcoconut5 жыл бұрын
I've never seen you use the Landau notations ( a_n = o( b_n ), a_n ~ b_n, a_n = O( b_n ) ) which make this exercise pretty easy without using derivatives ! Is this not in use in the US ? Because we use it a lot in the French system, and I must say, they're very useful !
@maxencen.95502 жыл бұрын
et honnêtement les comparaisons de suite sont bien plus élégantes
@jeromemalenfant66226 жыл бұрын
Or, at 7:18, instead of using l'Hopital's rule a second time, you can just bring the -1/x^2 in the denominator into the numerator as -x^2.
@ozzyfromspace4 жыл бұрын
Actually that generates an e*(inf - inf) type situation again. But for what it's worth, I considered that too for a few seconds before realizing this. Best wishes friend 🙏🏽.
@112BALAGE1127 жыл бұрын
I have never seen a limit where using l'hopitals rule twice leads to the result.
@ponirvea7 жыл бұрын
He used it four times; at 11:04 the limit evaluated to -1 by applying l'Hôpital's rule twice more
@monzur19477 жыл бұрын
Ahmad Fares that's not using l'Hôpital's. It's just using the fact that all the terms of x with power less than the highest become insignificant as you go to infinity.
@JensenPlaysMC6 жыл бұрын
What rule is this btw? for the insignificant values of a power less
@carly09et6 жыл бұрын
This is the same as turning it into a sequence and using Supersums watch a Numbephiles' video before this the logic is the same. chain l'hopitals ==> Supersum :)
@agfd56596 жыл бұрын
@@JensenPlaysMC if you want it more formally, I would factor out the x^2 from the top and from the bottom, reduce them and notice that the top is equal to -1 and the bottom approaches 1, so you can take the limit without a problem now.
@reetasingh16797 жыл бұрын
Tried running a code to check this limit, and somehow the limits start blowing up after 10^9 it seems... Does Python not support the amount of precision required for the limit to approach -e/2?
@Mar1847 жыл бұрын
Yup, there is no way to accurately evaluate (1+1/n)^n for large n with ordinary floats. You could import the "fractions" module to utilize Python's arbitrary precision integer arithmetic by letting it treat it as a fraction - then you have perfect precision for that part, but of course the runtime will explode completely and quite quickly instead. And you still don't get any further since you can't express "e" as a fraction, so the e*n part will become inaccurate either way. A more promising approach is the "decimals" module. You just have to set a custom, really high amount of decimal digits. for "d" decimal digits, you should be fine for something up to just shy of n = 10^(d-1).
@reetasingh16797 жыл бұрын
Mar184 Thanks for the detailed answer! I will surely be checking out the 'decimals' module
@reetasingh16797 жыл бұрын
Doggy Jr Actually no, the answer is definitely -e/2. Like I said a month ago, I tried writing a program to test the limit because I was unconvinced too. But remarkably the program gave results close to -1.35 for values of n as large as a billion.
@italolima8556 жыл бұрын
Put It in a Scientific Calculator with n=10^9
@reetasingh16796 жыл бұрын
Doggy Jr Fully agree with you... But that wasn't my issue. My issue was with accuracy. The limit worked perfectly for relatively high values of n. At a certain point the limits started to blow up. I get that the number we are storing in the program is finite and not exactly equal to e. But we could still use a whole lot of decimal digits of precision to achieve the answer.
@xauriclegaming8654 Жыл бұрын
Hlo sir I am big fan of yours from Nepal could you please solve the important question from undergraduate scholarship of Japan that is mext Scholarship program some questions are feels hard
@cameronspalding97925 жыл бұрын
I would have used ln(1+x)=x-x^2/2+O(x^3) to work out an approximation of ln(1+1/n)
@alre97666 жыл бұрын
Visually if we graphed the 2 functions F(x)=(1+1/x)^x and G(x)=e.x, at the infinity G would have a 1.359140914 lead
@sohammakim9178 Жыл бұрын
If you want to know the derivative of (1+1/x)^x you can take the derivative of e^(xln(1+1/1x)) which is the same thing that he got on the screen
@zahari20 Жыл бұрын
If you want to differentiate such things, better make the substitution t = 1/x in the limit. When x grows to infinity, t approaches zero.
@GunSinMovies6 жыл бұрын
is it really acceptable to just throw l'hopital's rule around like this before checking if the condition for it even apply?
@jceepf5 жыл бұрын
In response to Andrea Parma, there is another way to get this. If one uses Sterling formula for the factorial, then the same results falls out without using L'Hospital's rule. n! ~ sqrt(2 pi n) * (n/e)^n The "e" falls out from rations of (n/e)^n for n and n+1 and the -1/2 from ratios of sqrt(2 pi n) and sqrt(2 pi (n+1) ). It is a round about way that uses integral results (ie Sterling) rather than derivatives (L'Hospital). PS blackpenredpen: I am growing a beard if I can get a nice chick like your announcer....
@GDPlainA3 жыл бұрын
Me: people will think you're up to something
@tonyhaddad13943 жыл бұрын
Sooooooo amazing !!!!!!!!!! I think its not zero beacaus when we have e.n its biger then( (1+1/n)^n )*n Beacaus that is already(e) but the first one we have to go to infinity to get (e) so its like a race when two people is the same speed but one of them begin to run first !!!!!!!!!!!!!!!
@johnnicholson88116 жыл бұрын
"derivative of (1+1/x)^x, it will be here soon, derivative of ln(1+1/x), it will be here soon"
@zohar991005 жыл бұрын
Checking the result: Put 1,000,000 or even 100,000 for n in the original lim and calculate. it gives -e/2 in a very high accuracy.
@tonypalmeri7227 жыл бұрын
I liked this, because ultimately you convinced me of something that was very counter-intuitive at first. I gained an important insight by watching this and thinking it through. The final convincing came, though, when I went to an online graphing tool and graphed that function, out in the area of x around 5000. Yes, I *know* that graphing is not the way to get the actual limit, but if something radically different was going on around x=5000 I would have been suspicious of the result and investigated further.
@chasemarangu7 жыл бұрын
0:03 at n=∞ (1+1/n)ⁿ=e but did you know that at n=φ (1+1/n)ⁿ=φᶲ?
@chasemarangu7 жыл бұрын
1:35 I had absolutely no idea so I did it on a graphing calculator and it appears to be -e/2 but let's think about this. Also I noticed on the graphing calculator that x·(1+1/x)ˣ−e·x is same as x·((1+1/x)ˣ-e) by the way lim (x→∞) all the time and so substituting already we get ∞·0 which means it could be anything on the interval [-∞; ∞] so we need to do more work, I am gonna do something really stupid now. Using the negative exponents we get x/((1+1/x)⁻ˣ) − e·x and we can do the really stupid thing now that is use L'Hopitals rule because I am calculus novice and don't really know what else to do so then we get 1/something − e·x and then you find out on wolframalpha that that something is too long to write out so you give up
@chasemarangu7 жыл бұрын
Actually, after watching the next ~45 seconds of the video it turns out I wasn't too far off you do use L'Hopitals rule lol only I did the wrong multiplicand switching to the denominator also I messed up because I didn't keep x times everything instead I did x·something − x·e well oh well
@chasemarangu7 жыл бұрын
in the end I am glad I did not do all the math that is a long time for one problem and my graphing calculator (aka cheating) guess was right
@returnexitsuccess7 жыл бұрын
Really cool video! Very surprised to see Santa Barbara show up though, come visit UCSB :)
@blackpenredpen7 жыл бұрын
returnexitsuccess I was actually there two weeks ago just for sightseeing. It's very pretty
@Djake3tooth3 жыл бұрын
4:55 can you apply l’hopital here even though (1+1/n)^n is an indeterminate form if you plug in infinity? Or can you just use the limit and say it’s e…
@jayantimajumder41512 жыл бұрын
Sir too algebra, that's not the issue but ina exam hall when the timer is going going gong, there has probality to be wrong So I use series expansion.it's really quicky way to solve..
@aymaniklayli2986 жыл бұрын
Nice solution and prefect you sir
@ЮрійЯрош-г8ь7 жыл бұрын
Thanks for the video. Why can't we using product and sum rule for limits show that it is equal to zero ?
@MuffinsAPlenty7 жыл бұрын
The product and sum rules for limits only apply when all of the limits you're splitting things up to exist and are finite in value. The problem with this situation is that the limits you want to split it up into are not finite. Both "terms" have a limit of infinity. You could recognize it as the indeterminate form ∞−∞ or you could factor out the n like blackpenredpen did and recognize it as the indeterminate form 0∙∞.
@ЮрійЯрош-г8ь7 жыл бұрын
MuffinsAPlenty oh, yeah, I understood, thanks for the answer.
@megacarlosloki7 жыл бұрын
Hey can you make some videos solving ITA-SP questions?
@proclubsjov35834 жыл бұрын
As x approaches infinity, why can we ignore the +2x on the bottom of the fraction?
@Bicho048305 жыл бұрын
11:37 You desappeared at the last frame. O_0
@danielrosado32133 жыл бұрын
Wouldn’t this mean that the value of the limit would be the same no matter what finite number you used in place of e!?
@robertj44244 жыл бұрын
If you use substitution x = 1/n, then you can get the final answer quicker: lim{x->0} [(1+x)^(1/x) - e]/x = lim{x->0} (1+x)^(1/x) [(-1/x^2)ln(1+x) + 1/x - 1/(1+x)] = lim{x->0} (1+x)^(1/x) [(-1/x^2)(x - x^2/2 + 1/x - 1/(1+x)] = lim{x->0} (1+x)^(1/x) (-1/2) = -e/2
@sinom7 жыл бұрын
I would have thought it was 0*n which is... Problematic...
@supercool13124 жыл бұрын
Sinom its not, because thats just 0
@kaizoisevil4 жыл бұрын
@@supercool1312 If this is a limit where n goes to infinity, then 0*n cannot be simplified to 0.
@infirmuxx6 жыл бұрын
Good math, as always.
@wolfram96697 жыл бұрын
Very good video! Thank you.
@tomasthemas6 жыл бұрын
In your final Limit, why do we omit the 2x+1 on the bottom? Doesn't that meant the bottom approaches infinity faster than the top?
@danielmiddleton60946 жыл бұрын
Technivally yes, but think about this. Infinity^2 is a lot bigger than 2 (infinity). Infinity times bigger, in fact. So it effects the outcome by basically nothing, so we can "essentially" get rid of it, leaving the x^2
@OonHan7 жыл бұрын
OMG So interesting
@pasawatviboonsunti90665 жыл бұрын
Plus e/2 in the limit, and multiply by n, then you get another limit to find.
@PsyKosh7 жыл бұрын
Interesting problem, thanks. Though am wondering: why rename n to x instead of just writing d/dn?
@blackpenredpen7 жыл бұрын
n is usually for whole numbers, so d/dn wouldn't make sense.
@87我是-h3u7 жыл бұрын
Psy Kosh *usually*
@PsyKosh7 жыл бұрын
Go wild and differentiate with respect to n anyways. I won't tell. ;)
@pierreabbat61577 жыл бұрын
I thought you were going to set x=1/n. That would put just x in the denominator, you differentiate it and get 1, and you just have to differentiate (1+x)^(1/x) at 0.
@jarikosonen40795 жыл бұрын
It could be correct, but could it be made without LH?
@shezanahmmed55823 жыл бұрын
Where do you get such type of problems? Please, can you suggest me?
@NO-ll4fp7 жыл бұрын
I never thought when n tends toward infinity that basically e times n minus actually e times n would be negative e on 2
@ahmedalmerza17074 жыл бұрын
So then is the limit form of "e" is actually an underestimate of "e" itself, given that the solution is a negative number?
@kaizoisevil4 жыл бұрын
Yes, it approaches e from the left.
@hydraslair47237 жыл бұрын
@blackpenredpen, can this be interpreted as if (1+1/n)^n approached e as fast as n grows to infinity? Or, equivalently, their difference goes to zero as fast as 1/n does?
@cecilhenry99087 жыл бұрын
This is very counter intuitive!!
@blackpenredpen7 жыл бұрын
Cecil Henry it is!!! I first thought it was 0
@marcelweber78137 жыл бұрын
And now everything makes sense and last weeks video weren't just for fun.