#help-39
1 messages · Page 274 of 1
The only way I can see applying it is by dividing numerator and denominator by x, then apply mvt on $e^{-x}$ to get $$\lim_{x\rightarrow 0} \frac{\frac{e^{-x}-1}{x}+1}{x}=\lim_{x\rightarrow 0}\frac{-e^{-t}+1}{x}$$ where $t\in (0,x)$.

That is how you’d do it
does the MVT come with the question?
what
yeah i think we'd use it twice
nope, just a suggestion
Well the easiest way will be to write e^{-x} = 1-x+x^2/2+O(x^3) near 0
This immediately gives you the answer
or just use L'Hopital
is this the series expansion?
i don't have the right to use the little o notation
I mean it's just the series expansion. I'm sure you know about it
yeah but i'm not allowed to use that either
the government has gone too far this time
i have a meme for this
i do but it's beyond the curriculum
How did you define e?
ikr 😭
pretty sure euler defined it
you mean the exponential function

lmao fr 😭
cwazy
khay shnu taf o shnu mvt
nfs chi hh
ewa shti lol
ok
@sand swallow Has your question been resolved?
(1+1/n)**n
As n -> infinity
Or (1+n)**(1/n) as n goes to 0
o men bead? baqa F.I
really?
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I suppose I use this?
augh, my favorite guy is studying stats and not abstract
Meanwhile all the stats people are in #help-6
XD
I really need to do well in stats 🙏
Interesting
Well good luck 🙂 I can't help because I only did applied version
I take offense to being called a stats person lmfao
No lol
yea, that's why I struck it out
There are no squares here
Yes pseudomathematician is more palatable good point 🙂↕️
mhm, and computing the joint pdf each time by hand is painful
like X_1+2X_2
Then (X_1+2X_2)-X_3
I will stab you 
and so on
Shouldn't you be able to do it all at once
lemme see if I've forgotten something
okay, got it
I just forgot some properties 😔
just need to use this
Or more generally, this
Oh
I got caught up in the words and didn't actually read the problem
I'm actually familiar with that 😂
$X_1+2X_2-X_3+X_4+X_5 \sim N(0,\left(2+4-2+2+2\right) \cdot 2)= N(0,16)$
wai
just a wider normal
also times 2 or times 4, you have std deviation?
2
the var is √2
oops
yea
maybe it’s late for me but isn’t standard deviation the square root of variance
yeah the main bit was this.
wai
For the next one I have $(X_1+X_2)(X_1-X_2)$
wai
$X_1+X_2 \sim N(0,2);X_1-X2 \sim N(0,2)$
wai
As the vars are indepdendent and Identically dist, we have $N(0,2) \cdot N(0,2)$
wai
what’s before is valid, but i disagree with this last statement as X_1+X_2 and X_1-X_2 are dependant of each other even though they are normal
mhm
makes sense
We can still find the joint pdf , it will just be more painful now I guess
tbh idk about this one, what i can say is that it can be negative
so it can’t be straight up a chi or smt with only positive outputs
Uh, I tried looking this up
smt we usually did in my prob course to figure out joint distribution is to start with P(X_1^2+X_2^2 < x)
but here idk if that’s computable
so You're suggesting $P(0<x^2-y^2<x)$?
wai
no I mean usually computing the joint CDF is simpler
oh one other dubious move i can see would to « condition »on the value of X_2, but i’m not 100% sure it’s legit
Hmm, in that case I suppose it's not really computible, but then I have to determine why
lemme see if I've missed something
oh wait
why are we trying to compute the pdf of the prdouct
instead of the sum
for sure in the stat litterature it has been studied and google gemini slop says it’s a non-central chi^2
MSE says the same
This is the best I could find https://mathoverflow.net/questions/89779/sum-of-squares-of-normal-distributions
A comment suggets it's related to Satterthwaite
tbh if you haven’t seen non-central chi in your class i would gamble on the fact the expected answer is to justify why the dist is hard to compute
I'm self studying for next sem, so It's fine I suppose
this is for my stats course 😭
oh ok so we can have some fun then cool
yup
I persisted with my idea of earlier
however the chi CDF is discribed in term of a incomplete gamma function
and that’s ass honestly
I don't get this
$f_{X_2}(y) = P(X_2=y)$
pola_touche
Like what have you written in green
oh I say it’s a normal PDF
yeah i apply homeomorphisms to my writing
anyhow from here we would need to spot out what distribution this is. That does not seems easy imo
We could just say it's a distbution with this CDF
i mean yeah, what would be cool would be to reduce this to the non-central chi cdf and call it a day
I just read about chi squraed yesterday, so I suppose I'll read a bit more about this and see if I get any insights>
hum, now that I think about it maybe trying to do this with the moment generating functions would be easier
but that’s just a thought
In probability theory and statistics, the moment-generating function of a real-valued random variable is an alternative specification of its probability distribution. Thus, it provides the basis of an alternative route to analytical results compared with working directly with probability density functions or cumulative distribution functions. Th...
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really silly question, but this isn't the product of the density functions is it
because it’s a random sample the joint density is just the product of the exponential densities
Like $\theta^3 e^{-\theta (x_1+ x_2+x_3)}$
wai
huh, okay
for x₁, x₂, x₃ ≥ 0 (and 0 otherwise)
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Why is it not -sqrt(72)?
B is the middle point of AC
Asking where the slope on the left intercepts
Also the angle between the slopes in 90
6sqrt(2) is the same
Yeah but the answer is -6sqrt(3)
Yeah first I did that but the answer is supposed to be E
Then I tried doing the formula for calculating the distance
That gave me 6sqrt2
hi
Hey
hru
I'm fine wbu
am i in the wrong channel
Yeah
im good
sorry mb
It's okay
@desert patrol what was your slope for perpendicular?
you have to do y1-y2/x1-x2
so should be the reciprocal
The opposite then
-sqrt3/3 for the negative
AC is between -6 and 2sqrt3
(0,-6) and (2sqrt3,0)
yes
The opposite is -sqrt3/3
yes
sqrt3 is -6 so what's 3?
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np
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Help, it's asking for the ratio of the colored triangles
!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
2
Can u explain wht u did...
@desert patrol Has your question been resolved?
I found one of the sides also the part where the sloped intersrct is a right angle
That would mean the answer is 1
Ih nvm
They are similar
You mean tht lines y= -mx+4a and y=mx r perpendicular?
Oh...
I suppose you could just find the coordinates of three vertices and find area using determinant method?
For the triangle whose one side is y axis 0.5 × base × height would work
I wasn't taught determinant
Find the vertices then use the distance bw a point and a line to find the height and distance bw 2 points to find the base.
Idk i would js do this for thr shaded triangle
Is it even possible
WdymTT can u not find the vertices?
This is all I could find
Ahh
Do u want to try this or no.
KARMA TEST
I can't find them
Tbh im awful at explaining :') but u have the equations for the lines and the vertices are their intersections.
Yep
because that's the point where they share the same y-coordinate. So they intersect.
You can find every vertex in terms of a and m
So its actually 90 degtees?
y = 2a and y = -2a
Yeah I dont think thats right
So the bottom part is 2a
i dislike the fact that the question diagram is misleading and not to scale. but dw
can you find the coordinates of these two verticies?
To find the coordinate of this vertix, you were on the right path when you set both line equations together.
From 2a=mx,
if you solve for x, remember, x is the variable, m and a are just some constant numbers.
x=(2a)/m.
You found the x-coordinate of this vertix (the orange dot)
you can plug in that x coordinate in either y=mx or y=-mx+4a to find the y-coordinate of that orange vertix.
@desert patrol I wonder if you're still here lol
good
nope. You see that the intersection occurs on positive x.
Oh this is not the slope its the coordinates
If it was supposed to be negative, you should also see an intersection in negative y-axis
nope, just the y-axis. m is the slope, but you realise that m got cancelled out when finding the intersection
Yeah
with that, and if you understand that the triangle is symmetric, like a 45-45-90 right angle triangle. Then you'll realise that the blue length is equal to this yellow length.
mx and -mx. Give me any random m.
if m=78 for example. very steep slope
but you notice that one equation will be y=78x and the other equation will be y=-78x + 4a
Yeah
I think I was wrong when I said it's a "45-45-90" right angle triangle, because angles 45-45-90 only happens if m=1. But either way, at the point of intersection, if you draw a vertical line through that point, the "two parts" of the triangle underneath will appear to be symmetric. I.e. isosceles triangle.
Yeah
is the other one also isosceles
since they share the same angles
30 60 90 triangle
?
I mean yeah it is the correct answer
Thx
a^2/2 = 2a^2/2 was what I got
So the ratio can be 1/2
And since 2 is not an answer
yeee!
😄 no worries, and sure
It asks for the area of the colored triangle, AD and BC have the same slope meaning they are parallel right? But I don't know what else I can do
brb 2 minutes, ill use chatgpt to translate and figure this out lol
kk
AD and BC are parallel.
Distance between AB is 4 units.
Find area of triangle ADC.
We see D is at height 10.
Fun question.
!status
What step are you on?
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2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
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5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
1
alright, I'll ask a few questions to get you started.
What do we need to find the area of the shaded triangle?
2 of the sides and maybe an angle for the formula
Maybe we can also substract something ?
Tbh I would really enjoy math if it wasnt for the exams
lol bare with me, I'm trying to figure this out too.
Your correct with what we need. My thought process is thinking that we should find the slope of AD, which would be the same as slope BC.
yeah, but I'm struggling to understand how we can find where C is.
something with angles maybe
Maybe we should draw parallelogram?
I don't know hoe that could help though
Can we say that this is a square?
nah doesn't look like a square. looks like a parallelogram
... yeah
<@&286206848099549185> I'll bring backup. I feel like we're missing something crucial xD
this?
Yeah
this
translation please
I should've checked it lmao
translated
your backup ain't crucial lmao
i say "fun question" but fail to solve it myself 
ya
Yup
Yoo guys
Hm.. so we doing ts?
gang gang
Yeah
---ive made an error-
A and B is not fixed
🙏
what are you trying to do here
are you asking the question or giving the solution?
I have question
!occupied
Yes
Someone else is already using this help channel. If you need help with a question, please open your own help channel/thread (see #❓how-to-get-help for instructions).
Ok
You should send it in one of the channels that are avalible
The one with the green tick
A is not fixed and B depends on A so B is not fixed either
so probably let $A$ have the coordinate of $(x_A, 0)$ which gives the coordinate of $B$ as $(x_A + 4, 0)$
1 divided by 0 equals Infinity
Yeah
and $AD // BC$
1 divided by 0 equals Infinity
So they have the same slope
cool
Which is negative
if we assume $x_A > 0$
1 divided by 0 equals Infinity
which it is lol
The shape is on the right though?
so what's the slope here
you can make a line(any line) here that passes through the point (0, 10) and then translate it to the right by 4 units to get a line for BC, after that you can get a length for BC and AD
slope = -10/a was found from earlier, ya
Yeah
i mean
only hope is to find the coordinates
so using the parallel then we can find the formula for $y_C$
1 divided by 0 equals Infinity
and hopefully $x_C$
1 divided by 0 equals Infinity
there's a formula for y_C? :o
isnt yc 0 since it is on the axis
since when do you say that $C$ is on the x axis
1 divided by 0 equals Infinity
it would be less than 4, not 4, because it's not touching the line BC, if it touches the line BC and is parallel to the x axis, then it'd be length 4
it isn't
nah, by y_C, we mean the y-coordinate for point C.
oh right! mb
AD can be equivalent to y=-x+10
BC can be equivalent to y=-x+14(translated to the right by 4 units)
wait doesn't the area for this vary depending on the slope or how steep it is + there's no conditions for C
is ADC a right angle?
It's not given
the problem doesn't have a specific solution(I'm guessiing this from what the panda pfp person has sent)
does C stop anywhere or is C just on that specific line?
oh wait
no nvm
height doesn't change along with that
but the slope does change the height of the triangle
by any chance do you know finding area by determinants?
No I wasn't taught and I din't think it's in the curriculum
k
alr I'll give this q the benefit of the doubt
let y=-x+10 be a line that has line segment AD(let m=-1 for simplicity sake), A would be at (10, 0)
this would form a 45 45 90 right triangle with O where the length between AD is 10*sqrt2
now, consider BC, since BC is parallel with AD, we can consider a 45 45 90 right triangle with AB as the hypotenuse, where the leg would be equivalent to the distance between AD and BC(or the altitude of the triangle ADC with AD as base)
this would then give us 4/sqrt2 or 2sqrt2, whhich you can then multiply to the 10sqrt2 earlier and divide by 2 to give you the final answer of 20
I don't see an algebraic way to solve this that isn't complicated asf
genius, but slightly annoying q. you choose A to be at (10, 0). That would never cross my mind
that doesn't matter diagrams suck
This line?
yes that line would be the leg of the 45 45 90 right triangle with AB as hypotenuse
Thanks
I knew for a fact that could be a square lol
That angle definitely looks like an acute but whatever
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@desert patrol do you know how to find perpendicular distance from a point to a line?
Yeah
Ye
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Let (A) be a set of positive natural numbers not exceeding (10^{2025}).
For a set (A):
- (A + A = {a+b : a,b \in A}),
- (A - A = {a-b : a,b \in A}),
- (A + A + A = {a+b+c : a,b,c \in A}),
- (|A|) denotes the cardinality of (A).
Determine which of the following statements are true:
A) If (|A + A| \le 5|A|), then (|A - A| \le 50|A|).
B) (|A + A| \le |A - A|).
C) If (|A| < 10^{1000}), then (|A + A| \le 10^{2024}).
D) If (|A + A| \le 5|A|), then (|A + A + A| \le 25|A|).
E) If (|A + A| > 10^{2025}), then (A + A + A) contains a number of the form (2^k - l) for some integer (k > 6000) and (l < 600).
is \le supposed to be \leq or is it just french...
what have you tried
$\le = \leq$
LY
tez z polski jestem
:)
nie mam pomyslu jak z tym zadaniem ruszyc, jestem w 3 klasie i mam wrazenie ze to co mialem w szkole nijak odnosi sie do tego
tak z inuticji sobie to rozpisalem i wlasnie na tym utknalem
anyone want to help?
It seems to involve additive combinatorics? There is a combinatorics theory channel below. If no one can help you maybe you can try that channel
@bronze pike Has your question been resolved?
@bronze pike Has your question been resolved?
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How do i prove this? I don't really get the problem intuitively
do you know Wilson's theorem
No
ok ignore that
anyways, here is a hint
||rearrange the product||
hint 2: ||pair elements with their inverses where you could||
what does that mean again...
the group is abelian, yes? you are free to group the elements in teh product $\prod_{g\in G}g$ in any way you like
add them with their inverses?
oh i thought it was like the operation of the group
What im basically saying is to group every element in the product next to its inverse in the product. e.g., $g\2g^{-1}$
Question now becomes: what does $g\2g^{-1}$ evaluate to?
the identity element
yeah
LOL
but also, this is true, but there is a catch
what is the catch
uhm
in your case, what happens if g = g^{-1}?
g is the identity element isnt it
Yeah this one is kind of just a "find the trick" question
g^2 is the identity element
oh righy
oh so it can only have one g
could you really have g*g
ergo if we multiply everything we end up with identity elemtns * g
right. so there is leftover
yeppie
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I want to find the strongly connected components of this graph
idk how to find the bigger ones, i could only find two, a-i and d-e
Are the bottom and top rows of vertices strongly connected
b is connected to h but h is not to b
@low matrix Has your question been resolved?
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i need help regarding lateral surface area, i am in 7th grade.
Hassan built a fence around a square yard. It took 48 meters squared of lumber to build the fence. The fence is 1.5 meters tall. What is the area of the yard inside the fence?
!show
Show your work, and if possible, explain where you are stuck.
So like the lesson I learned is like, solving for rectangular prism's volume
And so I'm stumped at what to do when faced with an area question regarding like
prisms/3d objects
well it's not regarding prisms
just treat this like how you usually would with a 2d geometry problem
this isnt a 3d problem at all
possible to be 13 during 7th grade
fyi im 13 and on 7th
i was out of school for a yr
bc a piece of debris struck my left eyebrow area and i had to get it removed
its alr, im just tryna get thru school...
wait so i just do like
area divided by the uh
height?
48m (squared) is area i think
what
no the area of a square is its side length squared
so you have 12^2 or 12x12=144
oh
by squared do you mean power of 2 or just the label
power of 2
oh alr
hold on
it says the heigh is 1.5
so we may need to divide 48 by 1.5 first
then do the rest
the wording is a bit weird
yea I think this is what it means
so it would be 32/4=8
and 8x8=64
but I don't know
lemme get confirmation
That’s what I got as well
huh
but like what do i do???
bc i gotta show my work and stuff and i dont wanna keep spamming this with the same questions
I think the 1.5 height was there for a reason so just take the 64 answer
wow its right whew!
ty!!!!!!
The area of a single piece of fence is 12. You divide 12/1.5 to find the length of a single piece of fence. The length of the fence is the same as the length of the yard
Since the yard is square you just do the length squared
its sorta weird tho since they gave the height and no width
np
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i completed my reasoning and logic for a question i was trying to solve in a test. i want feedback and to know if my logic is incorrect or not. grade: 7th
!da2a Just post your question and we can give feedback!
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question!
a volume word problem is:
Q: "Jamie wants to know the volume of his gold ring in cubic inches. He gets a rectangular glass with a base 3 in by 2 in and fills the glass 4 in high with water. Jamie drops his gold ring in the glass and measures the new height of the water to be 4.25 in.
What is the volume of Jamie's ring in cubic inches?"
My answer and logic:
to find it, understand that when his ring is placed in the water, it displaces an equal volume of water and pushes it up. so the volume of his ring would be the incremental volume of which the height increased. what is the incremental volume? to find the incremental volume, multiply the length (3 cubic inches) by the width (2 cubic inches) by the height amount increased (0.25). so to find the incremental volume, we do 3 times 2 times 0.25. 0.25 is the same as dividing into fourths, or into 1/4 or one-fourth.
so 3 times 2 is 6, times 0.25 is 1.5, as half of 6 is three, half of three is 1.5. so the incremental value is 1.5 cubic inches.
any feedback on my logic and reasoning?
Sounds good to me
any ways i can improve it?
It's the same as my reasoning but expressed slightly differently
My reasoning was volume at the end must be volume at the beginning + change in volume
The change in volume must be the volume of the ring
Multiplying, volume at the end = 3*2*4.25 = 25.5 cu. in.
Volume at the beginning = 3*2*4 = 24 cu. in.
Therefore volume of the ring = end volume - beginning volume = 25.5 - 24 = 1.5 cubic inches
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idk
uhh regardless
pls help
uhhh can you graph the function y=|3x+2|+... mentally?
yessss
ok so can u take a pic of a rough sketch of it?
||wouldn't finding the maxima and minima ( local and global) be enoug||. Instead of a sketch
||uhh if certain assumptions exist then yes||
namely ||end behaviors both go towards the same infinity|| and ||convexity||, both of which happen to be true in this, but i feel like a sketch is just more intuitive
Fair.
Na, bruh, because I
am from the web.
bhaiya kya bolre ho
i mean ki main website sai hu
phone sai nhi tho photo nhi bej paunga
okay but does ur sketch have 'two' branches
yeh
so when are there two possible values of x corresponding to y/k?
its going to be, when we can draw a horizontal line y=k
and it passes through the function exactly twice
yess
okk ok
i understand
thank youu
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If f:A->B is surjective , g:B->C is surjective.Show that g o f is surjective.
.
Kindly check this proof .
help?
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Looks correct
Though in the final part better remove “any” in “any b in B”, just say there exists a such that…
^ You could do this a lot more concisely though:
Civil Service Pigeon
Alternatively, if you're fine with image language, you can one-line this:
Civil Service Pigeon
Btw, if you put . at the start of your first message, then the bot will assume that you're not claiming the channel (which is bad)
Consider (x-1)(Σk x^k). And you should claim a vacant channel
This is their channel actually
Cuz the last person added a . Before their message

Oh, the first person added .
Please repost this in another channel without the dots lol
.close
Guys, what is this type of example called? (Need a topic name)
What should I do ...
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My doubt has been cleared.
Consider (x-1)(Σk x^k)
Who can tell ???
@analog walrus Has your question been resolved?
poor justin, he came into my channel by accident
and now even after he claimed it he was kicked out by bot lol
its called math, primarily a quadratic equations question ... Also claim a non-occupied channel next time
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what have you tried
let the og polynomial be ax³ + bx² + cx + d Let's assume they get og polynomial by adding so the polynomial to which they added derivative MUST be ax³ + (b-3a)x² + (c -2(b-3a))x + d - (c - 2(b-3a))
But it's previous operation is subtract
So it must be
ax³ + bx² + but for third terms we need (b-3a)as coefficient of x² which cannot be because we have b-3a as as second term so we need b
(At the beginning of a class, the teacher wrote a third-degree polynomial on the blackboard. Then the students alternated among themselves, each performing one of the operations with the polynomial written on the board (which was then substituted by a new one):
(a) add to the polynomial its derivative.
(b) subtract from the polynomial its derivative.
At the end of the class the polynomial initially written by the teacher reappeared on the blackboard. Prove that at least one of the students made a mistake.)
That's right
Also this
Is this logic right
Base case
Getting same polynomial by 1 operation - obviously they made mistake
Assume that if we getting poly after n operations, there's an error
Now assume we did it in n+1 trials
And prove that it's not possible
Hence, no matter how many operations u do, it's never possible to get same poly back
oh do the students have to keep switching operations? so one does a then b then a etc?
Consider the matrix $\begin{matrix}0&0&0&0\1&0&0&0\0&2&0&0\0&0&3&0\end{pmatrix}$
Cogwheels of the mind
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Prove that the power of this matrix won’t be +/- identity
Using Jordan form I think
Sorry I meant product of multiple I+A , I-A can’t be I
Where A is this matrix
(I+A)^m (I-A)^n doesn’t equal I
Still, Jordan form
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Wdym 🤔
Let's say we start with poly f
Then let's say first student chose addition so he will write f+f'
Now consider f+f'=g
So next student MUST subtract because alternate operation they are performing
So he will write g-g'
So on
yes that's what i meant, thanks
Since your operations are linear, corresponding I+A and I-A respectively. Then their canonical form will be I+J and I-J where J is the Jordan form of A
Am sorry but am in high school 😭
So I was expecting a solution that fits into my syllabus
Ik math doesn't work like it, but I would like to solve it with resources I hve
Also, can u check my solution
@naive zinc @random ermine
I see no reason why the second operation has to be subtraction. You assumed there are two operations performed?
they're going backwards i think
Nope
The operations are in alternate manner no.
YEP
Exactly. So your reasoning fails
How
so in the 3rd last polynomial, what's the coefficient of x^2?
You said the second operation has to be subtraction
And you just said yourself it doesn’t have to be
2nd last polynomial according to u is (in the case last operation is addition)
ax³ + (b-3a)x² + (c -2(b-3a))x + d - (c - 2(b-3a))
i haven't checked this btw but i'll assume this is right
Anyway I can’t think of another method except using matrix
i think we're first considering the case where the last operation is addition
We split it into cases
First We assumed that we got the og polynomial by adding derivative to whatever is written there
But since operations are alternating
Second last operation MUST be subtraction
This has to be the Polynomial
Because we want the og polynomial by adding it's derivative to this 2nd last polynomial
So you can check by additing derivative, we do get out og poly back
yep and u also need to make sure it's the only such polynomial g st g + g' = f
It is it is
Because....
While adding or subtracting derivative, coefficient of x³ remains same
Instead while adding derivative x² is ALWAYS ADDED with 3a so coefficient of x² in second last poly SHOULD be b-3a
By such reasoning we can find coefficient of x and constant too
alr
Anyway, I don’t have to split cases since I+A commute with I-A the canonical form of A is J ((k,k+1) entries being 1 others 0), n addition, m subtraction done gives you n-m, nC2+mC2-nm, nC3-(nC2)m+n(mC2)-mC3=0. Should give you m=n=0
Yeah nC2+nC2-n^2=0 does give you n=0=m
If translating to elementary staff I guess you can prove those two operations commute with each other
Hmm..will look into ur method too
Ig that's only the better solution
let g = f + f'
g - g' = f + f' - (f' + f'') = f - f''
let h = f - f'
h + h' = f - f' + (f' - f'') = f - f''
so the order of operations doesn't matter
and because addition adds 3a to the coeff of x^2 and subtraction subtracts 3a to the coeff of x^2,
the number of times each operation is done is the same (n=m)
Matched
n-m, nC2+mC2-nm, nC3-(nC2)m+n(mC2)-mC3. These three should be 0. First condition matched
so you're basically doing f --> f - f'' multiple times to get f again
so you can reduce the problem to this 1 operation
this operation keeps subracting 6a from the coeff of x (the coeffs of x^3 and x^2 remain unchanged)
a != 0 so contradiction
@subtle crystal hopefully my solution is comprehensible
so you're basically doing f --> f - f'' multiple times to get f again
- And - goes alternatively
yes
actually this works even if the + and - ops don't alternate
and can be in any order
Why did u consider such an operation tho?
which one
The operation which u considered which only subtracts from coefficient of x
that's f - f''
which is because of this
@subtle crystal Has your question been resolved?
Umm gimme some time I'll process this
Really sorry, I am a bit slow
I'm confused
Define by A the operator f←f+f'
A^-1 • A = f-f''
now define B:=A^-1•A
B^-1•B = f+f'''' = f for cubic f?
x^3
+f' = x^3+3x^2
-f' = x^3-6x
-f' = x^3-3x^2-6x+6
+f' = x^3
x^3-3x^2-6x+6 +(3x^2-6x-6)=x^3-12x not x^3
@subtle crystal Has your question been resolved?
Damn dude
Understood it now
😭😭😭😭😭😭😭
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please teach my...in it we have to find elimination matrix
are you familiar with row operations yes or no.
ok so do you need more help or not
no...
ok
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How would one go about solving this
$f(xy)=f(x)f(y)-f(x+y)+1$
If given $f(1)=2$, find $f(10)$.
d1 shitposter
is it something involving testing x=1 y=1 and x=-1 y=-1
x=y=1 gives you f(2), try find f(2) and f(3) and see if there is a recursion or pattern @hollow sonnet
right
Let y=1
just moving the things around
f(10) seems to be 11
can someone double check
thanks
Correct
d1 shitposter
can I multiply the inside by x to multiply the outside as well
f(x+1)=2x^2+3x type shi
Let y=(x+1)/x you see x=1/(y-1)
a function is a thing that maps values of x to y right
f•T=g then f=g•T^-1 actually (on the suitable domain)
T here is a linear rational transformation, your case T(z)=(z+1)/z
Two sets X and Y, a function from X to Y is a subset F of X times Y such that
- any x in X there exists y in Y such that (x,y) is in F
- for any (x,y) and (x’, y’) in F, if x=x’ then y=y’
Given such F, for any x in X, by 1) and 2) there exists a unique y in Y such that (x,y) is in F, we denote this y by f(x)
X times Y here is a cartesian product or something right
Cartesian product
Have to
makes sense
Intuition explanation comes later, if necessary. Without definition any explanation is void
A function from $X \rightarrow Y \subset \subset F \ mid$
d1 shitposter
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i used IBP in the first step
to get integral nk (1-x^k)^n-1(x^k) from 0 to 1
and now idk what to do
@toxic lichen is it still wrong
it is correct now, any ideas?
nope
well clearly u need an I_(n-1) term
what can u do with the x^k
rewrite it somehow
x x^(k-1)?
that doesnt really help tho
okay try to split it into 2 terms
one with I_(n-1) and other with In
(1-x^k)^n-1 x^k and ur saying use IBP again?
no no
well u have x^k and u want it gone, now can u write it using 1 and (1-x^k)
oh (x^k -1 + 1 ?
Integration by part you should have obtained a recursive relation for I_n
thats what im trying to obtain..
yeah 1-(1-x^k)

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mb
kings rule would be a good idea if there was no x^2
I'm guessing you take each integral and apply kings again except for the x² one
why queens rule?
i mean queens
well they're all the same
whats the same
apply kings rule, then expand the quadratic, you will get -I in the resultant integral
so you can move that to the other side and get 2I = stuff, I = stuff/2
wont u get +I?
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$xf(x)+2f(-x)=-1$, find $\sum_{i=1}^{100}f(\frac {1}{i})
d1 shitposter
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Do we know anything else about f? And is f defined for all complex numbers?
try plugging in -x maybe
You actually can solve the expression of f, try replace x with -x to obtain another equation
it's not stated but my course content would make me assume f is defined for all R
brilliant idea
thanks
oh crap I forgot an x
$xf(x)+2xf(-x)=-1$, find $\sum_{i=1}^{100}f(\frac {1}{i})$.
d1 shitposter
yup
3xf(x)=4
f(1/x)=4x/3
then it just becomes the sum $\sum_{n=1}^{100}\frac {n}{3}$ right
Good
d1 shitposter
this sum should be uhhh 5050 right
Yeah
thanks
Np
last question of the day
Let f be a function such that
$f(\frac {x+1}{x})=2x+3$ \
For all $x \in \mathbb{R}$, let set A and B be subsets of R, where $D_f=\mathbb{R}-A$, and $R_f=\mathbb{R}-B$. Express $A \cup B$ in roster notation.
Can’t understand
Uh
d1 shitposter
I mean can’t understand mathematically
the notation here is domain and range of function
Ouhhh
is the -1 for matrix (1,1),(1,0) supposed to denote a division linear transformation or something
^-1
Yeah
I see
T(x)=(x+1)/x corresponds to the matrix (1,1;1,0)
I'll need to study up on that
Don’t have to though, certainly make things smoother
(Ax+B)/(Cx+D) should the correspond to the matrix (A,B;C,D) right
Yeah
makes sense
Matrices / ~ where A~ kA for some constant k
I don't understand functions enough for this yet
F maps to G by applying a linear transformation to f
which means that f can be obtained by applying the inverse linear transformation on g
There is no map that maps mappings to something. All those are just composition
f•T=g
(composition of f and T)=g
composite with T^-1 in the front of both sides
f=(f•T)•T^-1=g•T^-1
(On a suitable domain)
i see
in this case, the transformation is the inverse of (1,1;1,0)
multiply g by inverse of function to get f(x)
where f(x)=3+2/(x-1)
sheesh
Yeah
Np
.close
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i have helped with this exact problem too lol
That's why I pinged, I read the chat...
lol
How many checkerboards are there in total
we have 4 cells, each with either red or blue
So ig its 16
yea
is this it
bottom line is wrong
did i miss one
that class should have 4 elements, and also you wrote the same one twice
only BRRB and RBBR?
i cant find the other two
what operation did u perfor?m
so just four classes?
what about RBBB etc?
oh
there wil be two more [RRRB] and [BBBR]
each will have four elements
yes
yes
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i’ve just been in this place before
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I am drawing the hasse diagram
Replace the top 12 by 20 and it's acceptable
Just a slight mistake
Aside from that the Hasse diagram on the right is acceptable
whyy tho
al my arrows are upward
10 clearly doesn't divide 12
10 * 2 = 20
that is why i did not conect 10 and 12
I assume the left one is your answer? Remove 5->20
why? 5 divides 20
You already have 5->10->20
oh
btw how do i know where to place the vertices
the diagrams i draw turn out to be ugly lmao
Also you should have 2 -> 4
i did
yes yes mb
but that is not my diagram hehe
i copied from the solution
mine is the left
Oh
By elements“rank” if your poset has some good property like polytopes. But in general I don’t think we can guarantee to make the heights reflecting their order
how could i know 2 and 5 are at same level
and that 25 is at the same level as 4 and 10
You couldn’t know in advance. Now that you know you can modify it
can i put 25 at the same level as 12 and 20?
Yes since they're all maximal here
12,20 and 25 are maximal?
You just guarantee one thing:
which is the greatest elemnt?
If x and y are adjacent , and x<y, then y must be placed above x
There is no unique maximum here. It's a partially ordered set
yeah cuz the arrows are upward
does this hasse diagram have a greatest element?
Elements having the same height, or one being higher can still be incomparable, it’s allowed
