/sci/ - Science & Math

How do I calculate this probability?
Here's my problem: My friends and I played card game.
There's 5 of us and there are 6 cards. 2 of them are "A" and 4 are "B". Each round we pick randomly 1 card.
What are the odd of me picking 3 times (rounds) card "A"; and what are the odd of me and my friend picking card "A" 3 times?

>tfw youre a 4.0 physics student with published research youd rather go to grad school for feminist studies

wow how the fuck did this even happen, guess i shouldnt have let that girl i had a crush on second year convince me to take a feminist studies class

I suffer from chronic illness, and though i've never heard of it before, this makes total sense to me.

People don't understand that you're not just being lazy, or that you can't get (or rather, keep) a job repetitively doing things that they've seen you do occasionally. You need some way to explain it to them.

It's just comical that this got named "spoon theory" because someone tried to explain it, and the nearest collection of small, similar objects was a bunch of spoons.

So I'm doing my last assignment for my linear class, which is all PDEs. I can solve the eigenvalue problem, figure out the form of the equation in Cartesian and spherical coordinates, set up the series and then Fourier it to isolate the coefficients... But I get the coefficients wrong every single time.

Like seriously, I don't know what the fuck I'm doing wrong, because it seems to be a different error every time. One had every constant term squared except one, one was off by a factor of five, and when I did a spherical harmonics problem, my coefficients weren't even remotely close to the solution. What the fuck gives? I can't figure out what I'm doing wrong here, and the error is different every time I do a problem.

Why are my coefficients so fucked, /sci/? I thought I understood Sturm-Liouville, but I guess not because I'm banging my head against a wall here. Are there any good books on PDEs y'all would suggest so I can not bomb my final?

>>6156954
>I am an optimist
>Even a though just a few light years, it would still be a 20,000 year journey.

Sup /sci/. I'm good at maths and horrible at physics, what can I do for a living that isn't soul crushing and still pays well?

>>5572821
OK, ok, great. So it's OK for these things to take time. I've tried my luck on doing something more formal with another proof, this one taken from some lecture on proofs in Nottingham University.
"Prove that for every odd integer n, n^4 - 1 is divisible by 16."
Here's what I got "formally" so far:

Prove that for any odd integer n, n^4 - 1 is divisible by 16.

Let n be an odd integer.
n can be written as e + 1, where e is an even integer, 1 less than n.
An even integer plus an even integer is an even integer.
n^4 = (e + 1)^4 = e^4+4 e^3+6 e^2+4 e+1
By the same token n^y - 1 where y is any positive integer is also even.

Prove that e^4+4 e^3+6 e^2+4 e+1 - 1 is divisible by 16.
e^p is even since any even integer plus another even integer is also an even integer.
xe is even since any even integer plus another even integer is also an even integer.
Therefore, e^4+4 e^3+6 e^2+4 e+1 - 1 is even.

To be even is to be divisible by 2.
16 is 2^4

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And then I just can't go on. I've got the idea that since it's n^4, it HAS to be divisible by 16 because 16 is 2^4, but I just can't put it on paper. Do you see my general problem now?

All that said and done, I'm growing a greater appreciation for proofs the more I do of them.

quick /sci/, does the set of sets that don't contain themselves contain itself?

what the fuck is a ring?

i'm in classes this semester that are far more advanced than anything i've taken before; and my number theory professor has been talking about how domains are special cases of rings and how fields are special cases of domains and whatnot; and i'm a little hung up on what the general case of a "ring" is.

is it just anything with addition and multiplication defined; with a multiplicative and additive identity? is there something else there that i'm missing?

it's really just something i've really been wondering about; because the textbook assumes i already know what they are; and it's not so critical to the class that i want to bother my proff for a detailed explanation; but i don't know any of you guys; so if i annoy you it's not a big deal.

help?

>>4591366
*So lets hope they are careful and don't try to make a lot of money really fast.