all solutions to 2^x-3x-1=0 (transcendental equation)

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Learn how to solve this transcendental equation 2^x-3x-1=0 with the Lambert W function! This is definitely not a regular math equation that you see in school!
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Lambert W function introduction: • Lambert W Function (do...
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22 окт 2023

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Комментарии : 183

@blackpenredpen 8 месяцев назад

so you want a VERY HARD math question?! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Rg3dBosfZ3Y.html

@Youtube_Stole_My_Handle_Too 8 месяцев назад

2:22 Learning is to eliminate enough unsuccessful paths. More of that.

@paltze 8 месяцев назад

Best math variables: α ❌ Fish ✅

@ropi314 8 месяцев назад

🐟

@samthedjpro 8 месяцев назад

Fish ❎ X ✅

@murariprasad8372 5 месяцев назад

Hehe I am your sister 😅😅😅

@Peter_1986 8 месяцев назад

0:38 "First off, we need to have a fish - I call this the _alpha_ fish!" lmao

@rogerkearns8094 8 месяцев назад

It's clear from the testing of easy candidate values that one solution is 0 and that there's another between 3 and 4. Interesting to be shown how to solve it properly, thank you.

@flawnel 8 месяцев назад

Testing of easy candidate values is the best name I've heard for "Throwing numbers at the function and see what sticks" :))

@rogerkearns8094 8 месяцев назад

@@flawnel Great, that's something. Cheers :)

@eldunari6676 8 месяцев назад

Plug n chug am I right

@rogerkearns8094 6 месяцев назад

@@eldunari6676 I prefer that to suck it and see. ;)

@arghamaji8234 8 месяцев назад

When you realise that x=0 is also "an" solution

@zimzimal8547 8 месяцев назад

Wdym “when you realise” it’s immediately obvious

@abhirupkundu2778 8 месяцев назад

@@zimzimal8547 not for everyone bastard

@griffinf8469 8 месяцев назад

“a solution”, not “an solution”.

@supernovaw39 8 месяцев назад

Baka mitai

@zihaoooi787 8 месяцев назад

@@zimzimal8547 no it isn't

@Maarttiin 8 месяцев назад

I just ran into your video, I remember following your channel ages ago, being a student and trying to figure out how to solve calculus exercises. Now I'm graduated, but still enjoyed the video, and it took me back to that time, living off of coffee at the library, sharpening my pencil and the table full of the residual eraser lol

@blackpenredpen 8 месяцев назад

Welcome back! Hope all is well for you : )

@JohnDoe-ti2np 8 месяцев назад

A nifty general trick to learn is that once you get 2^x = 3x+1, you can use the substitution y = 3x+1 to get rid of that annoying constant 1. This gives you y = 2^((y-1)/3) = 2^(y/3) * 2^(-1/3) or 2^(-1/3) = y*2^(-y/3) = y*e^(-y(ln 2)/3). Then multiplying both sides by -(ln 2)/3 gives you the desired "fish" z = -y(ln 2)/3 on the right-hand side.

@lambdaprog 8 месяцев назад

TBH, we have become computer assisted scientists and engineers with ever weakening math muscle. I once was tasked to setup a monte-carlo for the aviation industry to estimate the lifetime of a jet engine. I remember I replaced the whole monte-carlo simulation by solving an integral with maxima (compound Weibull). I wondered why no one in the R&D thought about it. Your video gives a clue.

@LucasDimoveo 8 месяцев назад

This is one of the big reasons why I want to be good at math

@colereynolds2080 8 месяцев назад

Physics of photonic crystals is the same way. Every paper published is all numerical simulations or calculations with no fundamental equations to guide the reader. Just hand waving, ad-hoc arguments. Currently in a back in forth with Physical Review A because their "expert" referee did a simulation and it didn't agree with our analytical formulation. I hope your work landed you some nice job security. You have a valuable skill.

@rogerphelps9939 8 месяцев назад

You were fortunate in having an amenable problem. Most problems are not like that.

@MrGreenElephantHD 8 месяцев назад

Most transcendental equations are not analytically solvable, so there is little room for “math” math. As others have stated, the overwhelming majority of problems are only solvable by approximation.

@kyriethegoat8007 8 месяцев назад

I get what you mean by "math" muscle. What do you think is the best way to train it?(a high school student wishing to enter the number 1 or 2 best engineer school in my country and who is passionate of maths)

@burningtime7746 8 месяцев назад

Glad to be able to get this one on my own, my working was nowhere near as neat and simplified as yours though

@gmjackson1456 8 месяцев назад

Nicely done!

@peterg76yt 8 месяцев назад

Is Lambert W really a function? I see the concept is useful and it's worthwhile giving it a name, but is it a function that humans can calculate?

@oddlyspecificmath 8 месяцев назад

I keep seeing it in things I ask WolframAlpha. It's starting to feel like I'm going to have to learn how to calculate using it :/ so interested in any responses you get..

@ZipplyZane 8 месяцев назад

It doesn't have an elementary form, so it can't be calculated exactly. But the same is true of functions like ln or sine. And just like with those, there are ways to get closer and closer to the exact answer. That said, just like with those functions, you're mostly expected to put W(x) into a calculator. It's just that most regular calculators don't have that function built in, so you have to use websites like Wolfram Alpha. In short, the productlog or Lambert W function can be useful. There just isn't any way to solve xe^x = a without it. It can'e be broken down into any simpler functions.

@carultch 8 месяцев назад

If by calculate, you mean express in terms of a finite number of operations of arithmetic, integer powers, and roots, then there is no way to do it. But if by calculate, you allow for techniques such as iteration and infinite series, such that you can calculate it accurately enough for your purposes, then there certainly is a way to calculate it. Steve has a video on it here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Qb7JITsbyKs.html

@maxrs07 8 месяцев назад

fixed point iteration method video plz

@carultch 8 месяцев назад

What is the backstory to Lambert choosing to call this function W?

@adrien9926 7 месяцев назад

I finally understand a video, im progressing thanks to you keep up the good work :)

@orterves 8 месяцев назад

7:37 Now I'm wondering if you can't shuffle the W(-ln2/...) contents with similar tricks (And presumably it has something to do with i?)

@Ninja20704 8 месяцев назад

I wonder, is there a way to get 0 as a solution using something similar to the first method of iteration? That would be interesting.

@hohuynhquocchuong4925 8 месяцев назад

Taylor expansion around x=0, because 2^x expanse is converge in R so the 2^x-3x-1 also converge. And when you expand the constant term is eliminated so the x can be sub out to equal to 0, but the remain infinitive polynomial is too complex to be reduced In fact the general: a^x - bx - 1 = 0 always have a root x = 0.

@aatos5392 8 месяцев назад

Except if a=0

@JSSTyger 8 месяцев назад

Well i drew graphs of y=2^x and y=3x+1. The intersection point is somewhere between x=3 and x=4

@kornelviktor6985 8 месяцев назад

Productlog is so useful.I don't know why they don't teach it in high school.

@elquesohombre9931 8 месяцев назад

It’s a bit useless in hs math for the most part, that and trying to understand it isn’t the most hs friendly when most people in highschool already struggle with other, more simple, concepts

@askandpushpaltiwary8537 8 месяцев назад

most calculators dont have it (i think) it also cant be computed by hand

@elquesohombre9931 8 месяцев назад

@@askandpushpaltiwary8537 well you COULD always use newtons method of solving an equation but if you don’t have 20 hours of time, then only some can be solved by hand. An example would be 2*ln(2) which is equivalent to ln(2)*e^ln(2) but that’s a very specific case and wouldn’t be practical at all so yeah.

@kornelviktor6985 8 месяцев назад

@@askandpushpaltiwary8537 thats a good point, but you dont need to calculate it. Its good to have the exact form not just the first three digits of an irrational (most likely) number

@kornelviktor6985 8 месяцев назад

@@elquesohombre9931 Well good work takes time🤣🤣

@Macieks300 8 месяцев назад

the fish function is my favorite

@esotericVideos 8 месяцев назад

This technique seems like it might be helpful for solving the collatz conjecture.

@yaomass3705 8 месяцев назад

x1=0, x2～=3.53767 by for loop

@heroasik5423 8 месяцев назад

in epsilon delta there should be simple epsilon/delta=f'(a)

@scarletevans4474 8 месяцев назад

To the people confused by the fish: don't worry, fish doesn't have to be real. I would explain more, if I could, but well... it's complex.👌

@Dark_Souls_3 8 месяцев назад

Hey where’s the sphere mic?

@dwaipayandattaroy9801 8 месяцев назад

✌️😁✌️( 2^x-3x-1) =0 Multiply both side with a 0 so, 0 = 0 ✌️😁✌️

@radupopescu9977 8 месяцев назад

You may want to solve this (other then graphically): x*4^(1/x)) + (4^x)/x -12=0; real solutions are 0.5 and 2...

@anupamamehra6068 8 месяцев назад

@blackpenredpen can you prove this : integral from 0 to infinity of (root x times ln(x)) / (1+x^2) dx = (pi)^2 / (2root2)

@vascomanteigas9433 8 месяцев назад

Using complex Analysis it is easy. A square Root combined with a logarithm means that Share a branch cut Over the positive real axis. Consider a keyhole contour with the complex function f(z) = (exp(log(z)/2)*log(z))/(1+z^2). The contour are composed by two straight lines and two centered circles. It is easy to show that Over the two circles the modulus of f(z) are bounded by: f(z)

@gianfrancodiazgamboa6512 8 месяцев назад

Isnt Lambert W function aproximated via fixed-point iteration? Or there's a way to find the solutions analytically. Also great video💯💯

@viliml2763 8 месяцев назад

Well it's easy to see that -ln2/(3cbrt2)=-ln2/3*e^(-ln2/3) so the zeroth branch can be found analytically in this case.

@TanmaY_Integrates 8 месяцев назад

What is the Integration of -cotx cosec²x? My book gives answer (cot²x)/2 (by u sub) but d/dx of (csc²x)/2 is also -cotx csc²x. Please reply

@MathNerd1729 8 месяцев назад

This is why the +C is important because (cot²x)/2 and (csc²x)/2 both have the required derivative [they just differ by ½ which you can show via trig identities]. Hope that helps! :)

@Ninja20704 8 месяцев назад

(cosec^2 x)/2 = (1 + cot^2 x)/2 = 1/2 + (cot^2 x)/2 The two answers are said to be off by a constant (1/2 in this case) which are considered equivalent as far as indefinite integrals are concerned due to the +c

@TanmaY_Integrates 8 месяцев назад

@@Ninja20704 thanks bro. This freaking formula, I totally forgot. As it was useless in our syllabus questions.

@TanmaY_Integrates 8 месяцев назад

@@MathNerd1729 thanks bro for the help

@mickelsantiagoquispenamuch4961 8 месяцев назад

at 7:36 is ln not log. idk if was an error or not because get the same answer

@thatomofolo452 8 месяцев назад

Linear equation

@user-xc3pg9bz8z 4 месяца назад

4:22 we there isn't base for the function as in the normal log Log base x W base x??

@GoodSmile3 8 месяцев назад

I love the fish gimmick

@makarayann5349 8 месяцев назад

What is W?

@memespy9415 7 месяцев назад

What if (for example) n=2? Does the W-Lambert function not also give a new value than? Or does it only give a value we already got? Or does it give no value at all?

@baconboyxy 6 месяцев назад

Little late here, but only the 0 and -1 branches can give real solutions so if n=2 you would get a complex one.

@somebody9232 7 месяцев назад

If A = 2023(10^n) + 1, where n is a positive integral, then can A be the square of an integral?

@beaue4187 8 месяцев назад

What happens if n = 1, or 2, or a fraction, or an irrational number, or a complex number?

@LilyKazami 8 месяцев назад

n=0 is the only branch that stays real for its entire domain, while n=-1 can give real answers within a certain range. The other branches will always give out complex results. The branches are distinct and don't have in between numbers. Long story short it's all about how complex multiplication works - those quantized 2pi rotations.

@anttwo 6 месяцев назад

Hello, great solution, but I didn't understand what does n=0, n=-1 etc. mean. Could someone explain?

@AB-Prince 8 месяцев назад

one fish, two fish, red fish, blue fish, alpha fish, betta fish.

@haithmahmed3588 8 месяцев назад

I love math

@wauict6234 8 месяцев назад

Can you try solving x^2 + 2^x = 0?

@JoaoPedro-cv7hn 8 месяцев назад

2😎🤙

@skagna 8 месяцев назад

@@JoaoPedro-cv7hn4+4=0? 🤨

@blackpenredpen 8 месяцев назад

this video is similar: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ndA0sF_0Rwk.htmlsi=YfV8rBOIopB6OK3F

@lima8615 8 месяцев назад

what is w?

@michaelbaum6796 8 месяцев назад

Great👍

@Mefrr12 8 месяцев назад

Innit like (2^x-3x-1)^x=0

@williamthompson5988 8 месяцев назад

Instead of writing it as -1/(3cbrt(2)), couldn't you have written it like (-1/3)2^(-1/3)? Then using the ln2 and a base change in the next step it would turn into (-ln2/3)e^(-ln2/3), which means the Lambert W would reduce it down to simply -x-1/3 = -ln2/3

@Rb_Drache 7 месяцев назад

You get -x-1/3 = -1/3 if you do that, in which case you only get x = 0 because lambert W identity works like this: W_(0)(xe^x) = x when x>= -1, W_(-1)(xe^x) = x when x

@bassem.al-ashour 8 месяцев назад

On the left side W((-ln2)/(3(2^1/3)) can be rewritten as W((-1/3)ln2*e^((-1/3)ln2)) which evaluates to (-1/3)ln2 This gives the zero solution

@blackpenredpen 8 месяцев назад

yup!

@sotocsick3195 19 дней назад

didn't you derive a formular for that?

@markmoore9486 7 месяцев назад

At a glance you know the answer is between 3 and 4. If 3 significant figures is OK create a spreadsheet and vary X from 3 to 4 in 0.001 steps. How is that different, really, from asking Wolfram Alpha to solve it? But it was a fun ride. 😅

@aquss33 4 месяца назад

me after bprp says: "Lambert W function", I know video'll be a banger

@rrr00bb1 8 месяцев назад

i like it!

@rrr00bb1 8 месяцев назад

was terminating it with log_2[1 + 3] intentional? but a graph of this in wolfram alpha.... 0 = -v + 1 + 3 log_2[v]

@kauanfsantos9112 8 месяцев назад

3^x+x=30, Solve the value of x thank you

@user-rn3oe4js7u 7 месяцев назад

I think this problem can be solved using calculus. Is it a correct method?

@user-iy6dt4xp5o 8 месяцев назад

0:02 me: what’s loy? 0:03 me: oh that’s just log

@Lohikaarme1984 8 месяцев назад

Isn't a zero also an answer? :]

@cardaroy3556 8 месяцев назад

oh dayum

@rogerkearns8094 8 месяцев назад

You must have missed it because the video does say so.

@Lohikaarme1984 8 месяцев назад

@@rogerkearns8094 ah, right, it really does in 7:37! I missed that. Also it's not written at the end as a solution, so that got me confused. ;)

@sanyalox01 8 месяцев назад

yes, and it is in the video

@Ninja20704 8 месяцев назад

@@Lohikaarme1984it technically still is in the final answer. When we wrote the final answer with the lambert W function, with an arbitary branch n, that is not one solution but an entire set of solutions, which does contain 0.

@mo.sa80 7 месяцев назад

دمت گرم خدایی❤

@stanislawek4829 8 месяцев назад

I've been thinking about this problem for long, could you make a video about it? Solve for a, b, c and d: a=bc+bd+cd b=ac+ad+cd c=ab+ad+bd d=ab+ac+bc

@Stereomoo 8 месяцев назад

I suppose to get a start on where solutions might be, I'd let a=b=c=d (since it's clear there exist solutions where this is true), so a=3a^2. 3a^2-a=0. a(3a-1)=0, a=0 or 1/3. Then loosen it a bit, a=b, c=d. so a=ac+ac+cc=2ac+c^2, c=aa+ac+ac.= 2ac+a^2. difference in those is a-c = c^2-a^2 = (c-a)(c+a), divide by (a-c) (only valid if a not equal c) to get 1=-(c+a), c = -a-1. back into the earlier equation, a = 2a(-a-1) + (-a-1)^2. becomes a^2+a-1 = 0, solutions are the golden ratio, a=-phi c=1/phi and then the other way around. The same kind of cancellation to get relationships works with all 4 variables (c-d = ad+bd-ac-bc = (a+b)(d-c)), it's just progressively messier to work back to quadratic equations. You'd also want to check the intermediate step a=b, c not equal d, and a=b=c, to make sure you find all solutions.

@TheKing-cn2ou 8 месяцев назад

why is't it x=0?

@thatomofolo452 8 месяцев назад

Constant

@blackpenredpen 8 месяцев назад

x=0 is a sol but there's another one a bit more than 3

@eugen-m 8 месяцев назад

❤❤❤

@fazilzaliyev9879 8 месяцев назад

Solving with graphics

@blackpenredpen 8 месяцев назад

or the fixed point iteration! : )

@technopanipuri3054 2 месяца назад

Him saying alphafish Me a chess player:😂😂

@aMyst_1 6 месяцев назад

You already made a video of creating a formula for a^x+bx+c=0 1month ahead just use that 🐟🐟🐟

@its_lucky252 8 месяцев назад

can't you just take the x root of 2^x, and the x root of 0=0. so x =-0.5

@atharvmali3132 8 месяцев назад

Me after I realise that 0 is also an answer 👁️👄👁️

@heinrich.hitzinger 7 месяцев назад

👁👄👁

@jameswoodard4304 8 месяцев назад

No. No, I do not want that. I don't know why the algorithm decided I *did* , but I don't. I want other people who want the answer to be able to find it. Congratulations! Well, done! Now never speak to me again Mathman.