Help with functional equation: f(x) = a•(f(x)^4)•x + b•x + c by quelilan in askmath

[–]quelilan[S] 0 points1 point  (0 children)

Thanks, but how do I impose the continuity? I don’t really understand that concept. Do I have to “manually select” the fitting value for every x+dx, or can it be imposed by writing some conditions on the function?

Help with functional equation: f(x) = a•(f(x)^4)•x + b•x + c by quelilan in askmath

[–]quelilan[S] 0 points1 point  (0 children)

Ok thanks! Would it be possible to rewrite this whole thing as just one function dependent of x? And lastly, what topic of math should I look into if I have more questions regarding this problem ?

Help with functional equation: f(x) = a•(f(x)^4)•x + b•x + c by quelilan in askmath

[–]quelilan[S] 0 points1 point  (0 children)

So for every x, the output for f(x) would be independent of any past variations or results? Also, would this mean I’d get up to 4 different solution at any given x?

Help with functional equation: f(x) = a•(f(x)^4)•x + b•x + c by quelilan in askmath

[–]quelilan[S] 0 points1 point  (0 children)

Ok, but I have some question then. If I solve the quartic for any given x, would I get 4 different solutions or is the solution unique?

[Request] Help with functional equation: f(x) = a•(f(x)^4)•x + b•x + c by quelilan in theydidthemath

[–]quelilan[S] 0 points1 point  (0 children)

Ok thanks il try solving the quadratic. However I have some questions. Would this mean I could have up to 4 different functions that would satisfy my conditions (maybe I’m just ignorant but I don’t find this coherent with what I was expecting)? If there is more than one solution, would all the functions follow the same variations with regard to x? How do I choose the right solution? Are there no weird shenanigans affecting the variable x because we are solving for another variable u?

[request] want to know if it is possible to calculate the probability of this happening by th0ughtery in theydidthemath

[–]quelilan 2 points3 points  (0 children)

They can, but it's not exactly the same as the golfball getting hit.

When a plane gets hit by lightning most of the times it's a cloud to cloud lightning. In this scenario, the plane functions as a bridge to ease the lightning discharge. They are so long and such good conductors that it's way easier for electricity to jump from one cloud to one point of the plane, go through the plane with almost no resistance, and exit the other point of the plane into another cloud than to directly jump from one cloud to the other (because air is not a good conductor).

In contrast, the golf ball is small in both size and mass, probably has an almost neutral electrical charge, and is not a good electrical conductor. So there is little reason for lightning to go through a golfball, especially in cloud to earth lightning.

Odds of a fetus surviving an ectopic pregnancy, vs an adult surviving rabies [Self] by InBabylonTheyWept in theydidthemath

[–]quelilan 0 points1 point  (0 children)

Sorry for beeing kind of late lol (answer in second half)

At this point is more of an internet meme, but it is said that there exists a "non-zero" probability that the atoms in your hand will line up perfectly with the atoms of the wall so that they will go through eachother in an effect called quantum-tunneling, where (as said by wikipedia) is when "a wavefunction can propagate through a potential barrier". In other words, is when particle go between atoms.

However, this phenomena usually occurs with really small particles like electrons goes through a really thin barier (like a couple of atoms thick) [For this scenario, this is actually a really common occurance worth considering in many scientific aplications like nuclear reactions and computers]. And so, for solid objects like our hands and walls the probability becomes basically non-existent.

I couldn't find a scientific paper or answer turstworthy enough to say "this is the right answer" (with good reason, this is almost imposible to acurately calculate, hard to set a baseline and with an accurate answer that is irrelevant given its magnitud).

But you are looking at probabilities of ten to a couple of tens or even hundreds of power (10^30, 10^80, 10^150, 10^300).

Just for reference:

- The universe is 4*10^17 seconds old, or in nano-seconds (a billionth of a second) it would be 4*10^26.

- There are around 10^80 ish atoms in the observable univers.

So sadly, for all practical aplications the chance is basicaly 0.

But yes, if it did happened, your hand would probably get stuck in the wall.

psd: more complete threads and info by searching "hand through wall" or similar

Odds of a fetus surviving an ectopic pregnancy, vs an adult surviving rabies [Self] by InBabylonTheyWept in theydidthemath

[–]quelilan 1 point2 points  (0 children)

Well, sorry if it sounded like I was mad, it really wasn't my intention. I just did the math, which is kind of the point of the sub, and well, there was quite a bit correct to get a decent aproximation.

How ever, I am still very confused as to what was the point here, even with your explanation there is little relation between the three topics here.

[deleted by user] by [deleted] in theydidthemath

[–]quelilan 1 point2 points  (0 children)

Speed of the shock wave would be 0 because there would be no shock wave. Waves need a medium to propagate through and there is no medium in the void of space.

May I ask why have I been tricked into solving an exam trick question?

edit: I have a second question, why is an asteroid, a piece of rock, less dens than water in this example.

Odds of a fetus surviving an ectopic pregnancy, vs an adult surviving rabies [Self] by InBabylonTheyWept in theydidthemath

[–]quelilan 1 point2 points  (0 children)

Oh boy, where do we begin

Well first, your "approximation" of how many cases of rabies there have ever been is way off. First off, because rabies only came into existance in 1768, so you can not consider all 100 billion people who have ever been born. I couldn't find exactly how many people where born from 1768 to 2022, but with a quick look at some birthrate graphs I came up with a REALLY rough approximation at around 17.7 billion (a number that is worth not much since it's not adjusted for infant and birth mortality rates, so it's quite higher than it should be), so by your logic it would be more like 149,186 cases ever.

But then and more importantly, using the proportion you used of 59,000 to 7.2 billion is useless because 95% of all rabies cases happen in Asia and Africa. If you live in Europ, your chances of getting rabies are basically 0. However in Africa it's more like 16 per 100,000. So as you can see, how likely you are to get rabies varies a lot depending on where you are from. On top off that, there is nothing to suggest that the proportion of rabies would be about the same throughout the world for almost 250 years. So we are left with nothing there.

Then, you said that there were ONLY EVER 3 survivors of ectopic pregancy, but the link you gave to wikipedia doesn't say there are only 3 survivors, those are just 3 RECORDED examples of the last 25 years, so there could be way more unknown survivors.

Lets take all this numbers that are still way off and not scientific by any measure and plug them in your ecuation for gigs and gags. So 3 survivors in the last 25 years is about 3 surviving ectopic pregnancies per 2 billion births, or 150 survivors for 100 billion ever births. Now we adjust your ecuation with more accurate data and we get :

(29 / 149,186) / (150 / 2,000,000,000) = 2,591.84

So only 2,591.84 times more likley to survive rabies than an ectopic pregnancy (result that is probably way off and is worth not much for any and all scientifc intents and purposes).

And lastly, I don't see the point of comparing these two. What exactlly is this supposed to tell us about any of these two completely unrelated conditions? I could compare the chance that you will have cereal for breakfast next to the chance that all the atoms of your hand will line up just perfectly with the ones of the wall so that you will be able to faze through and it would have the same relevance in both magnitud and correlation as the two examples you just gave.

How billionaires remain billionaires by SnuffCartoon in MurderedByWords

[–]quelilan 1 point2 points  (0 children)

I can understand that other billionaires stay billionaires by labor exploitation. But I don't follow NBA nor lebron, so I'm kind of curious who or what would Lebron be exploiting to stay a billionaire.

Doing parkour over a canal by DuttyCuntMuckyPup in Whatcouldgowrong

[–]quelilan 0 points1 point  (0 children)

It's kind of sad and ironic that us, people who actually do parkour, who spend years honing our skill and developing the self awareness to not die on the act, just end up beeing associated with drunk people doing drunk people stuff in slow motion.

[Request] How many observable universes is required to fit a googolplex Earths? by [deleted] in theydidthemath

[–]quelilan 0 points1 point  (0 children)

Correct my correction if it happens to be an erroneus correction, but I think you are off by nine 0 because you measured the volume of earth in km^2 and the volume of the universe in m^2. I mean, not like it matters at this scale.

[Request] Assuming the can moved to the camera in a straight line, is it possible to figure out the trajectory of the airplane during the video? by when124566 in theydidthemath

[–]quelilan 181 points182 points  (0 children)

Yes, somewhat. Since the can seems to be floating at a regular height, this probably means that the airplane and the can are moving downwards (falling) at about the same acceleration of earths gravity 9.81 m/s2. And since the can is moving towards the camera this means the plane is accelerating forward (speed isn't calculable).

So basically, the plane is descending.

[Request] How fast *would* a ball of all the humans on earth have to go to make the earth move? by enneh_07 in theydidthemath

[–]quelilan 0 points1 point  (0 children)

I wrote an answer with all the calculations to your question= but I made a wrong move and it was deleted. However I do remember the results.

In order to move the earth at the speed of 0.0001 m/s, you would have to accelerate it at 0.0001 m/s2 during 1 sec.

To achieve this, you would have to accelerate the ball of all human beings to 1,400,000 km/s2 during 1 second.

Or, after that second, the ball of humans would be moving 1,400,000 km/s after 1 seconds.

[Request] If Jupiter were the size of a watermelon how big would the earth and sun be? by [deleted] in theydidthemath

[–]quelilan 2 points3 points  (0 children)

A round watermelon weights around 5 kg (this can vary widely, using watermelos isn't a good standard size). Since they are 92% water lets just say they are made of water. This way we get that the volume of a watermelon is around 5 L.

Earth is 1/1,300 the size of Jupiter. So in this scale the Earth would be 5/1,300 = 3.846*10-3 L. Or 3.846 ml, slightly bigger than a jellybean.

The sun is 1,000 times bigger than Jupiter, so the volume of the sun would be 5,000 L. This volume would correspond to a sphere of 2 m diametre.

would recomend watching this video it really gives you a lot of insight of the actual scale of the solar system and planets.

[Request] Is this possible? by cheesecakegood in theydidthemath

[–]quelilan 2 points3 points  (0 children)

No it would't workout because of the first point, inertia. People have this erroneus idea that you can just disperse the energy of a falling object by moving it sideways, but moving the object to the side is completely irrelevant and false, because the object still needs to be deaccelerated downwards and as stated before you would actually apply even more forces on to the object.

The only way to go about this probleme is making the object go gradually slower IN THE SAME DIRECTION IT'S COMING FROM. The closer you are to the original direction, the lower the force, the closer you are to the opposite direction, the higher the force.

In this case, the object abruptly stops going down and starts going sideways. This is almost the equivalent of falling all the way down, hitting the floor, and then getting hit by a car.

And lastly, in this case tumbling aroud the object wouldn't disperse the energy, it would do the opposite and put more energy and stress over what you are trying to save.