Stupid questions thread - sqt

How does it generally work?

I've heard it's a very anal process

Journals often are. You send it in following their instructions, get reviewed, get rejected, try for another journal (or if it wasn't a hard rejection, revise it to meet their requirements of you), repeat the process, until you get in somewhere. But it also depends on the journal you're going for.

Is nofap detrimental to your health? I know the benefits have proven to be a meme, but are the detriments memes too? I ask because it's so much simpler for me to cut out masturbation, but I'm worried i'll get asscancer.

Does anyone have the art of problem solving books on pdf? Sorry for asking here but have been searching for days and I have 0 money.

Was the point of the Riemann Zeta Function to slap as many weird things together as possible and look at what they do?

Given a random number over a given amount what's a good way to suggest prime factors?

>these units put a man on the moon

if it's an even number then it is divisible by two

that's about all you're gonna get

The way I understand the sequence of math courses...
>Calculus 1,2,&3
>Differential equations.
>Linear algebra.
Then what? What courses come next?
What fields of math study are the ones we know the least about? All the other stuff is really old, so what's new in math?

or if it ends in 5 or 0, then it's divisible by 5

I've sat next to an economics professor in an international flight and we talked about academic publishing he one of the things he told me you have to do to get published is pay the journal and pay a team of referees to peer review it, and it ain't cheap.

Can someone explain to me how to solve this question?

In this scenario:
dot (x-x1, y-y1, z-z1) = x-x1 + z-z1 = 0

But since they said at distance 2 from the origin, does this imply x-x1 + z-z1 - 2 = 0?

which would mean x-x1 + z-z1 = 2

why is there a 2 root 2? also they didnt mention x1 or z1 just x+z, how is this possible? x1 and z1 are not zero..

Doing Project Euler and have a probability question (# 493):

Given an urn with 70 balls, with ten balls for each of seven colors, twenty balls are taken out without replacement.
What's the expected number of distinct colors?

I know the way to do this would be to take the expected value of the following expression:
X = random variable representing # of distinct colors
E(X) = (1*0, because P(only one ball is 0) ) + 2* P(2 colors) + 3 * (P 3 colors) + ... + 7 * P(7 colors)

My question lies in figuring out P(n colors). I know that it would be more complicated than something like (20 * 19 * 18 * ...)/ (70 * 69 * ...) because it's possible to get ten balls of one color first then get the next ten balls of a different color.

I made a small script that simulated this problem, and I got the answer to be about 6.382 , but I need to know how to calculate the probabilities.

Thanks in advance!

That's a fair point. That can vary wildly too. Some charge several thousand, some have a few hundred.

how do i solve this?
the other figure is in my reply

just for clarification, i'm stuck on part c

Don't know if this is the place to ask, but I haven't received any emails from Caltech about their decision, even though they apparently got released recently. In fact, I never got any emails from them whatsoever, even confirming my application submission. Did I fuck up?

You might have... Try sending them an email about the status of your application

Yeah, just finished doing that. It honestly doesn't bother me too much, since I had such little hope of getting in anyway, but knowing that I may have had a chance, and lost it because I made a mistake like a dumbass, kills me a little

If it makes you feel better, transferring is a thing... Just make sure to not fuck up your freshman year.

Good luck buddy, I'm rooting for ya

I tried to explain this in the other thread. Did you see my reply? Anyway, I edited the old pic to make it more clear. It looks kinda shitty because I'm writing with a mouse, but it should still be legible.

>But since they said at distance 2 from the origin, does this imply x-x1 + z-z1 - 2 = 0?
No. Why do you think that?

>also they didnt mention x1 or z1 just x+z, how is this possible? x1 and z1 are not zero..
What you're looking for is an expression that describes all the points in the plane. If you represent these points as vectors, then you can write a vector equation (see pic related). All these vectors have their tails at the origin. This is why you must subtract v from x (in the pic) to get the plane shifted parallel back to the origin, because only the vectors in the plane passing through the origin are perpendicular to v. That's how I make sense of it.

I don't get it, why are you scaling by two, also if you normalize (1,0,1) doesnt that give you 1/(root 2) * (1, 0 1)?

I dont get why (1, 0, 1) -> root 2/ 2 (1, 0 1) -> root 2 * (1, 0 1) in your pic.

I can understand the rest though

Also apply heat to increase vapor pressure

I've lost half a gallon of DCM from not-so-tightly capped bottles, so as long as you can wait a bit you'll have no trouble removing the solvent. But releasing DCM in the atmosphere is something you should be ashamed of, as I was.

en.wikipedia.org/wiki/Rotary_evaporator is how a chemist would do it. Basic distillation setup will suffice (use a warm water bath as heat source, and efficient cooling).

And don't even think about pouring the used DCM down the drain when you're done: it infamously clogs pipes.
Also it's not nice: safety.vanderbilt.edu/waste/chemical-waste-sewer-disposal.php#forbidden (section 2.a. DCM = Methylene chloride)

>why are you scaling by two
Because that's how far the plane is from the origin. You need a vector with the same direction as (1,0,1) but scaled to have a length of 2. This only matters for the v subtracted from x. So (x-v) can been dotted with (1,0,1) instead of v, and you get the same result (notice how I ended up throwing away the sqrt(2) factor in front of the parentheses in the second to last equation).

>1/(root 2)
That's the same as sqrt(2)/2.

Oh ty I see what you did now.

I think I found a way in which makes more sense to me though but I can't tell if its consistent and logically correct do you mind telling me if this was a fluke or it makes sense?

Taking the normal vector n=(1,0,1), we know that since in a plane equation, as long as our normal vector is normalized we should get n . p = 0, but in this case we don't know a point and dont need one since we have the normal vector which are the coefficient of the plane equation ax+by+cz = d.

However we know the LHS, our plane equation should be 1x + 0y+ 1z = 2 since we know its 2 units from the origin.

But our normal vector was normalized, so our original normal vector must have been already divided by root 2 to get the (1, 0, 1) meaning we must multiply both sides by root 2 to find the actual distance from the origin to the plane.

x + z = 2 root 2 should be the logical conclusion.

Does that make sense? Or is it nonsense

>ax+by+cz = d
>our plane equation should be 1x + 0y+ 1z = 2 since we know its 2 units from the origin
d is not the distance of the plane from the origin in that equation.

Well, unless (a,b,c) is normalized. If that's what you're saying, then yeah, that's right.

bullshit. stop confising people fagot

Find the least whole a with which the equation f(x) = a has exactly 3 fucking roots IF (pic)

I have no fucking idea.

Is Vacuum Energy the same as Dark Energy?

If so why does it cause the metric expansion of space?

I have 2 equasions and 4 variables.
Am I able to solve that?
If no I need proof because pic related

Answer is -11. For a moment I thought this was non trivial.

Let's say I want to find out the latent heat of some oils...

Is the method for determining the latent heat of oils the same as the popular method for ice? (e.g. atmo.arizona.edu/students/courselinks/fall15/atmo170a1s2/online_class/week_4/LH_ice_expt/LH_ice_expt.html)

Add all the non-divisible by 3 digits in the number, and if it's divisible by three, the whole number is divisible by 3.

Does the prime factorization of an even number (4,6,8,10,12,14,...) always contain the number 2?
I know that uneven numbers don't have to or maybe even can't.
Is there a theorem about that?

An even numbers definition is that its written in the form 2*x = ... so yes.

Thats the most stupid question so far.

>Does the prime factorization of an even number (4,6,8,10,12,14,...) always contain the number 2?
yes

>I know that uneven numbers don't have to or maybe even can't.
uneven numbers can't have a factor of 2, otherwise they'd be even

>Does the prime factorization of an even number (4,6,8,10,12,14,...) always contain the number 2?
Yes, because they must be divisible by 2 to be even.

>I know that uneven numbers don't have to or maybe even can't.
They can't. By definition, odd numbers can't be evenly divided by 2, so 2 cannot be one of their factors.

Not sure if bait, but just think. God damn.

Maybe I should drop out of university

Depends on your major.

Computer Science, 6th semester

when you're considering the factorization of any number, then you're talking about multiplication.
any even number has the form 2*a, where a can be literally any integer you like. As long as the 2 is there, that number will be even. If there is no factor of 2, then the number will be odd. This is because factorization deals with multiplication.
Now, a number can be the sum of two and a bunch of other numbers, like x = 2 + 3 + 4 + 5 + 6 + 7 and not be even. The even numbers in the sum will sum to an even number, and the odd numbers will sum to 1) an odd number, if there is an odd number of them or 2) an even number, if there is an even number of them.

i hope this helps. you get good at math by doing a lot of it, so you should probably start doing more math.

kek I wrote a raytracer in the 4th and a physics engine in the 5th how can you be this stupid in the 6th

And how are the classes going?

So I'm trying to learn some chemistry on Khan Academy, but I just can't seem to figure out a few problems that assume existing knowledge...

Why does a neutral fluorine atom usually gain 1 valence electron when forming a fluoride ion?

How do I found out what is the electron change for a specific element?
Is it a memory thing? Do I need to memorise it for every single element or group?

It seems that group 7A has +1, while 1A has -1, 3A has -3, and 5A has +3...

Is this what I need to memorise?

Also, if anyone has good links to learning material for chemistry, please post.

Is it safe for my boyfriend to keep his laptop on his lap? Does it cause infertility/ED/cancer?

It's been a while since I took chemistry, but here goes nothing

>Why does a neutral fluorine atom usually gain 1 valence electron when forming a fluoride ion?
It's a lot more energetically stable for an atom to have a full valence shell. Because Fluoride has seven Valence Electrons, it is really easy for it to gain one more electron and complete a shell

>How do I found out what is the electron change for a specific element?
>Is it a memory thing?
Yes and no... Every atom in a column (for columns not in the transition metals or lanthanides/actinides) will have the same charge. All the alkali metals (column 1) will have a +1 charge, all the alkali earth metals (column 2) will have a +2 charge, and so on. Things get weird when you get to nonmetals because that's when covalent bonding tends to take place. In that case, the charge of an atom depends on a situation.

>Also, if anyone has good links to learning material for chemistry, please post.
If I remember correctly, Veeky Forums has a torrent list of useful textbooks for all subjects, so just look for that torrent and look up the chemistry section

Thanks. But do you mean transition metals btw? I think I read something about them being different

Oh sorry I'm retarded, I misread.

I don't quite get the nonmetals part then

(# of combinations of 20 balls with n distinct colors) = (# of ways to select n colors from 7) * (# of combinations of 20-n balls from a pool of 9n balls) = 7Cn * (9n)C(20-n)

You can normalize this to get the probabilities.

Explanation: Consider the task of assembling an arbitrary combination of 20 balls with exactly n distinct colors. There are 7Cn ways of selecting the n possible colors, hence the first factor. Once you have selected the n colors, this fixes the colors of n out of the 20 balls in the combination. The remaining 20-n balls can be arbitrary so long as they come from the reduced pool of balls of one of the n fixed colors, i.e. they do not introduce "new" colors.
This reduced pool has size 9n (starting off with ten balls from each color, then removing one in the first stage), so there are (9n)C(20-n) ways of selecting the remaining 20-n balls.

The answer simply lies in the periodic table trends. ( it is quite easy to learn a will be very helpful)
To answer your question tho, we can rely on the octet rule ( which hold true all the way up to second semester Orgo)
the octet rule state that element tend to "want" having their last shell complete i.e. Have 8 electron this the name octet.
That explain the inertness of element that already have 8 valence electron (noble gas). Element that are very close to the octet state (halogen with 7 valence e ) really need that extra electron that why they tend to gain electron ( a rule of thumb is that non metal gain electron).
In the case of alkali and alkali earth metal they respectively need 7 and 6 e to gain the octet status, that is a very long way. So they simply get rid of their electron end become cation ( example Ca has 2 electron on its last shell l, instead of gaining 6 more it just get rid of the 2 and now Ca 2+ have achieved the octet status )
I hope it'll you get it. Of course things can get very complicated and i left a shirting of stuff out but this should help you :)

Alright, thanks mate. I can't say I fully get it yet, but I'll keep on working on it.

>partial fractions with squared denominator
the bane of my existence can someone ffs help i have no friends

(-10x^3-2x^2)/(x^2+2)^2=(Ax+B)/(x^2+2)+(Cx+D)/(x^2+2)^2
(Ax+B)(x^2+2)+Cx+D=10x^3-2x^2
Ax^3+2Ax+Bx^2+2B+Cx+D=10x^3-2x^2
Ax^3+(2A+C)x+Bx^2+2B+D=10x^3-2x^2
A=10, 2A+C=0, B=-2, 2B+D=0

How would I show this?

im confused by the concept of showing that "the moment about all points is 0" for a system being equilibrium... wouldn't that mean i have to take the moments of literally every point in the system? It's just something i can't really get my head round

p choose 1 = p

x^p-y^p
=(x-y)(x^(p-1)+x^(p-2)y+x^(p-3)y^2+...+x^2y^(p-3)+xy^(p-2)+y^(p-1))
= (x-y)(x^(p-1)+x^(p-2)x+x^(p-3)x^2+...+x^2x^(p-3)+xy^(p-2)+x^(p-1)) mod p
=(x-y)(px^(p-1))

p^k divides x-y and you have the extra factor of p there so p^(k+1) divides x^p-y^p

you'll bust a nut like a madman when you break it, that's for sure

This is the one I had in mind

sprott.physics.wisc.edu/pickover/guidec.html

It doesn't mention money at all so I think it's free

Thank you for the answer!

So I got as far as making combinations of all the possibilities, but didn't really realize you could do a combination (essentially I had 7Cn * (number of possibilities,... Didn't realize this was numerically equivalent to (9n C 20-n) ), so I feel I was fairly close to the answer, but I definitely needed that last push.

The only thing is that (and I might be implementing the calculation incorrectly), when I run it in a C++ script that calculates the answer, I get about 6.055, but when I plug it into a Matlab script that simulates about 100,000 runs of this, I get the answer is closer to 6.382. I'm tempted to believe the Matlab script is closer to the actual probability.

I am definitely getting really close to the answer, but I'm still the slightest bit off

Here's a link to a pastebin with the two scripts/programs
pastebin.com/HA7NSnyU

The least whole number is 0. Because the polynomial is of degree 3, there will always be 3 roots. You didn't specify that the roots be real, but they all are for f(x) = 0 anyway.

>asked for a whole number
>gives a negative number
baka

>Also, how long did it take for somebody to figure out the square root of i? Was it known immediately after the concept of i was developed?
[math]
e^{i\pi} = -1
\\
e^{\frac{i\pi}{2}} = i
\\
e^{\frac{i\pi}{4}} = \sqrt{i}
[/math]
Pretty trivial desu

Thank you user, i want to return the favor what can i do for you?

Can anyone please help me with this? Where is my mistake?

What's the easiest baby's first Abstract algebra textbook for someone with only highschool Algebra? Is there a Abstract Algebra book that doesn't assume more than HS Algebra?

Hungerford is the most babby's first algebra book that I know of

Thanks. I'll take a look at it. Hopefully its approachable for someone who's last math class years ago was HS Algebra.

Hey guys, could anyone show me a concise and tidy proof for part (b)? pic related of course.

My attempt:

If Σ*(aa)*n Σ* where n ϵ N, then there exists some trace which is a precise state q0, ... , q3 which is accepted by the machine M.

Similarly, if there is some accepted state, then the trace should consist of the sequence q_0, 𝛿(q_n, a), 𝛿(q_k, a), q_3 where n and k are intermediary states of the automaton which means that the a string is accepted iff it contains an even number of a's

>patrick bateman what do you think.jpg

Actually I realize
> q_0, 𝛿(q_n, a), 𝛿(q_k, a), q_3 where n and k are intermediary states of the automaton
Is definitely not right, can't really come up with a concise way to put it

thanks doc

I vaguely remember my 11th grade Biology teacher talk about Brown's molecular motion. I don't remember any details, but she talked about how air leaves your room through the window, but is then replaced in equal amount by air from outside. But when i check wikipedia, it says nothing like that.
What's up with that?

Also, assuming what my biology teacher is true, should I open my window and take a fan and point it outside the window, to rapidly replace the air in my room?

Best approach to study with books?
I write down definitions and shit only?

I dont know how to be more effective at studying. Usually I do examples only, no writing down shit.

Presuming this is about math/physics:

First and most important thing is to make sure you understand every word of every definition, not only what you're defining but why it's defined that way.
Once you have a solid understanding of the bedrock definitions the only thing that will build understanding is working through things with pencil and paper. Try to work out yourself as much of the main text as you can instead of only reading it; the body of the book is just there to direct you and help you along.
And do the problems, of course.

bump

it's so fucking obvious.

a two state (q0, q1) automaton where q0 is initatial and final state

arrows are

[math]
q_0 \rightarrow_b q_0\\
q_0 \rightarrow_a q_1\\
q_1 \rightarrow_b q_1\\
q_1 \rightarrow_a q_0\\
[/math]

Yeah, I'm studying math and physics
>First and most important thing is to make sure you understand every word of every definition, not only what you're defining but why it's defined that way
You mean making questions like "How", "Why" and "For what purpose"?
I ask these questions when I found a tricky problem, but I just memorize definitions.
>Once you have a solid understanding of the bedrock definitions the only thing that will build understanding is working through things with pencil and paper
Yeah, but I dont have time to do every single problem on textbook (lectures, part time work am e shit).
>Try to work out yourself as much of the main text as you can instead of only reading it; the body of the book is just there to direct you and help you along.
>And do the problems, of course.
Thank you.

Wrong

I'm learning how Coulombs Law effects Alpha Particles

I googled about it, and from some sources it says that Coulombs is both the force of charged particles (pos or neg) divided by square of distance (just like gravity).
Does the collision in this formula allow for situations where it's neg/neg, pos/pos or is it just neg vs pos?

I ask because I'm unsure if even neg/neg or pos/pos is possible, because they'd naturally repel like magnets anyway, wouldn't they?

how did this old man do it??

youtube.com/watch?v=l789l6np-qA

Is there an integral for arcsin(arcsin(x))? Wolframalpha doesn't respond when I query it.

So the complex plane and 2 dimensional coordinate plane are both similar in what you can do with geometry in them, but how much exactly do they overlap? Is it just a matter of some things being easier to do in one vs the other?

Particles of like charge can collide. But when particles collide they're getting close enough that the other forces aren't negligible.

Holy shit retard.
GRAPH THE POLYNOMIAL.

That is literally how you solved this.

Also, whole means the integers which includes negatives.

What is the name of the function such that f(x) = x^x

If the value of an item is $50 but you pay $200 dollars for it why do people say you paid 4 times as much as you should have paid when its only an extra $150, which is 3 times the items value, not 4?

well just saying x^x seems clear and concise enough for most purposes...

if you eat two hamburgers why do people say you ate twice as much as your brother Andy when you only ate 1 more burger than him, which is 1x

Exactly, Andy would have had to have eaten -1 burger for it to make any sense.