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but then the inner circle part would be principal
oh
wait what
no this doesn’t make sense
the first shows |z-4|<4
0<|z-4| simply excludes the point at 4
so i don’t have to find a series for it?
i don't know about laurent series
because in these examples, the graph is always split into two or three
note the eg for 3) is not done, I can show the rest tho
yea i’m not sure how to solve this
<@&286206848099549185>
cause you cant change it to a geometric series if its not a simple pole right?
omg i cant even watch youtube videos im pretty sure you cant just have a constant here
hm? looks like a partial fraction decomposition
oh yes
thats my bad im remembering smth wrong
its only if you expand it out that you have to do bx+c
ah
or like in form (x+b)^2
i think there's a special rule in that case
but pls how do you do this
do i understand example (1) correctly?
when |z|<2, the principal part of the laurent series is 0
when |z|>2, the analytic part is 0
also I think you can split into two parts you have 0<|z-4| which is principal part and |z-4|<4 which is analytic
but Im not sure if you can change into geometric series cause one of the poles is power 3
no i dont think so
but for |z|<2, you've written f as a series with z^n, which should comprise the analytic part, no?
and that series is meant to be the laurent series?
@tribal temple hii
both the analytic and principal part is the laurent series
yeah maybe i'm missing something
so for example (3), when 1<|z|<2, do you have f as the sum of 2 series?
or is it still just 1 series like the other examples on that page
i imagine it will have 2: one for the analytic part and one for the principal part
oh it seems like you only need to find expansion when z=0
for this question
because
in this example, since the singularities 1 are inside the area i guess it doesnt have to be expanded? not sure why tho
(z+1)/(z(z-4)^3) is undefined when z=0
how can you find an expansion when z=0?
sorry worded it wrong, 0<|z-4|
the singularity at 1 is not inside the area 0<|z-1|<2
I'll send a photo soon dw
all right
i think that's because the examples are finding the laurent series in as may domains as possible.
the question you posted only asks you to find the laurent series in the domain 0<|z-4|<4
no im stupid its the same thing as eg3. both annulus
just wait ill send a photo
yup
yes but presumably eg3 solves it for different domains
0<|z-4|<4 is an "annulus" but the central hole is only a single point
@tribal temple can you explain how to do this question
^
(If you give me a while I can try? Just had to go out for a while so don’t have my notes with me
)
ok, thank you!
in the video you're watching, z=1 is not a simple pole, right?
did they use an approach other than geometric series?
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I have like 3 sources telling me what to do in very different ways, and now I'm confused. Should I do the derivative first thing on the equation, or? @~@ And if so, should you not go past the point they did in the 2nd pic? I originally did and got -12x-8x^2+6x^3+9, but that was wrong according to another calculator T~T
Are you the kind of person who tries to avoid the product rule?
As is often the case with math, there are a couple ways to solve it
I do try to avoid it, but failed here xD
that's where I got the -12x thingy from
Ig I could just stop at where they stopped, and do the whole plugin thingy 🤔
Is there a way you can rewrite f(x) to avoid having to use the product rule?
I'm guessing f(1) is not the answer
Although I think the derivative you found using the product rule looks correct, so you could just use that
:D yay
What does the derivative mean?
slope of the tangent line
ah oki so that's where the point slope comes in
I seeee
ok I might've been overthinking this xD
justpossibly
That’s easy to do with math
I'm good with manipulating point slope and slope int, I can do the rest of this, thank you :D
You’re welcome
I was very unsure about the derivative's correct-ness, ty for checking it :')
have a good afternoon :)
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When determining sequence convergence or divergence and I have (-1)^ncos(npi) can I just bound cos and then dct it with something that has one as a placeholder for it?
@umbral cave Has your question been resolved?
I personally can't help you, but there's a rule saying that after 15 mins of no response, you can ping the helpers ping :)
wdym by dct here ?
you can just compute cos(n pi) explicity, it's simple enough
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!noans
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
5 plug in me kya aata he
Try rationalizing the denominator
could try using the conjugate
but can i use i am currently on class 11th my sir told use it for 12th
use Conjugate
oh ok, then you probably need to rationalize yes as others are saying
yes
you don't need it. Rationalize denominator will be the play. If you know how to do that
l'hopital would work, but tbh with radicals, the work involved would not be radical 
thank u guys finally got the answer
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You need to set the derivative of that to zero, to find critical points
2
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
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I think it's E
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The I will just put values and check
Yah for the second question you can also adopt this strategy, it's very quick @upbeat plinth
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Do you know deeivatives
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Otherwise just follow ankit's advice, same for the second question, find its derivative
hello im new in server
Ok
What do you want
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spider-man pjs
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reduce the powers
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Lololol
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f(x) = x^2 - 4x + 7
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f’(x) = 2x - 4
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what
$\frac{x^3-4x^2+7x}{x} = \frac{x^3}{x} -\frac{4x^2}{x} + \frac{7x}{x} = x^2 - 4x + 7$
knief
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The theta in the bracket means it’s in the fourth quadrant right
yes
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when we have a row or column that repearts in a matrix in linear algebra
does that mean theres no solution?
so i can just parametric them basically
<@&268886789983436800>
no screenshot necessary for future reference, we can see deleted messages
oh ok
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Hi, I am want to show that for $A = {x \in \mathbb{R} \mid x^2 < 2}, (\sup{A})^2 = 2$.
My work: Use trichotomy to prove a contradiction in other two cases where $ (\sup{A})^2 > 2$ and $ (\sup{A})^2 < 2$.
(i will refer to lub as z) First assume that square of lub is greater than 2. that means lub is greater than sqrt(2). then, take $\epsilon = z - \sqrt{2} > 0$. Then, for $w = z - \frac{\epsilon}{2} < z$, since $z$ is lub then $w \in A$. Then, $w^2 = (z - \frac{\epsilon}{2})^2 = z^2 - z\epsilon + (\frac{\epsilon}{2})^2
Basically I aim to show that there will be an upper bound smaller than $z$ if we assume it to be greater than sqrt(2) and there is a least upper bound which is greater if we assume $z$ to be less than sqrt(2), but i am not sure how to flesh that out in the details.
shell
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i know that i want to find that if z is the lub then if we assume z to be less than 2 and take w > z then we want to show that w is in A (which contradicts the fact that it cannot be in A if z is to be the lub) and similar for z being greater than 2
just not sure how exactly to execute the idea
@low stream Has your question been resolved?
The idea is to show that sup(A)^2 >= 2 and sup(A)^2 <= 2. Call M=sup(A), so first suppose M^2 < 2. The idea to contradict this is to find a real number x > M such that x^2 < 2. You will have to consider the interval (M^2, 2)
yes i understand that and my approach was to assume, say, M^2 > 2. then, M > sqrt(2) and we can take epsilon = M - sqrt(2) > 0. then, w = M + epsilon and therefore w > M but then i wasnt sure how to turn this into w^2 < 2
or sorry i meant w < M for w = M - epsilon
then i wanted to show that w^2 > 2
which implies w is not in A
which implies z is not
lub
Firstly, I think the point of this exercise is to show that sqrt(2) actually exists, so we should probably not use it in the proof. If we assume M^2 > 2, the contradiction we are looking for here is that there exists a delta > 0 such that $(M-\delta)$ is also an upper bound for A, as then M would not be the least upper bound. I think this is what you are trying to do right?
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yeah i mixed it up sorry
thats what i wanted to do
then i was going to show that this quantity squared is greater than 2 which means it is not in the set
but the answer key uses sqrt(2)
and answer key doesnt really make sense to me
Okay yeah they aren’t actually giving you epsilon in terms of what I have called M. But the overall idea is that if M > 2, then there is something just below that satisfies x^2 > 2. And on the other hand, if M < 2, there is something just above that satisfies x^2 < 2. In the second case, M is no longer an upper bound
ii get the concept but i dont really get how the epsilon comes into play
maybe that means i dont get the concept idk
I think they have skipped some working to show you what they have done. We are just trying to quantify this small nudge from M. If I want (M - delta)^2 > 2, then I just expand this bracket and try to rearrange for delta in terms of M
Ok so we nudge down to show that there is a least upper bound smaller than M right
Yes that’s correct
and we get to that conclusion by showing that if we take z^2 > 2 and w < z then we find that w^2 > 2 ( because we assume that the lub^2 is > 2) that this contradicts the fact that z is the lub
Yes but be careful with wording. We are saying given z, there exists a w < z such that bla. The goal of this part of the proof is to construct this w and show it satisfies that property of w^2 > 2
right yes
so when we take w as z minus some epsilon and find its square, im not sure how they find that the square is greater than 2
Yeah this is not a given and your proof just shoves it under the rug by saying “when epsilon is small…”
If you wanted to be rigorous you would have to say “epsilon must be this small”
That’s the idea of the proof
im not sure then why they take epsilon to be z - sqrt 2
that. seems arbitrary
or is that the whole point
that they inadvertantly aim to contradict the fact that epsilon is greather thgan 0?
when it is actually equal to 0
Yeah the point is that if z is not equal to sqrt(2) we have a positive epsilon distance between them, work with this, get a contradiction
It’s a fairly common idea
ah i see
i get that part but im not sure how the computation works out to getting w^2 > 2
If you just think about it completely concretely with a number line the contradictions become clearer I think. If the lub is < sqrt(2), then the midpoint must have square >=2, but this is absurd
e.g. suppose 1.4 is the lub for A
We know sqrt(2) = 1.414….
So this logic would say that 1.41^2 > 2
But this is just not true
ok so in the case where lub > 2 if we say lub is 1.5 is the lub we can say like 1.45 is less than the lub but 1.45^2 is also greater than 2 right
Yeah exactly
and we can do this infinite times because sqrt2 is not in the rationals
makes senes
well ig we. can do this infinite times if sqrt2 waws in the rationals
but we would never get an answer since it is not
I don’t know what you mean by infinite times, just this always works if you assume either lub < sqrt(2) or lub > sqrt(2). This has nothing to do with sqrt(2) being irrational, I could do the exact same thing with sqrt(4)
yeah i meant like we will not get an actual answer, ik we can do it infinite times for anything
Okay yeah, the point of these proofs is that I could choose M to be anything and this would give me the recipe for contradiction
right yeah
but i dont really udnerstand the symbolic version in the answer because if w^2 is greater than z^2 ( a number which is greater than 2) minus a positive number, that doesnt mean w^2 is greater than 2
are we just assuming epsilon is small enough to make this true
But how small is that positive number
Yeah i think so
As I said, your solutions are not fully detailed
yeah
There is a way to be completely convincing
i assume thats beyond the scope of my class
No when I learned it in an equivalent class they supplied a proof
i see
can i ask another question
my professor gave this weird proof for showing that set of rationals whose squares is less than 2 does not have a least upper bound in rational numbers
this seems like a very inelegant way and it also doesnt really make sense to me
Yeah tbh it is quite a lot of jargon to get your head around, it would take me a while to fully digest. What you could do to prove this fact is use what you have just done above with showing sup(A)^2 = 2, and use the uniqueness of supremum. We already know sqrt(2) is irrational, so this is a proof
But the principle of this argument is very common. Assume for contradiction, conclude either that it is not an upper bound, or not the least upper bound
yeah my initial thought was to just use what i did above and then we know sqrt2 is irrational but i think this proof assumes the same but gets to the conclusion in a different way
Yeah so the strategy is sort of the same, instead of nudging by a real number delta, they are nudging by a small enough 1/n, which ensures that we stay rational
is this the archimedean property
Yeah it is
these notes are weird it introduces the property after this example
Yeah that’s weird, it’s basically one of the first properties of R you should learn
No worries, hope it is at least a bit clearer
yeah helped a lot was stuck on this for a while
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Both the poisson and normal distributions are able to approximate the binomial distribution
My question is, how does one decide between which approximation to choose?
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the linearization is the tangent line at x = a
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ye
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the linearisation is an approximation of the function at the point, so it's not going to be exact
you need to differentiate tan aswell
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L(x) ≈ tan(-pi/4) + sec^2(-pi/4)(x+pi/4)
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L(x) ≈ tan(-pi/4) + 2(x+pi/4)
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,w tan(-pi/4)
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Am i just incorrect or their integration variables are incorrectly placed?
shouldnt it be dydzdx under their configuration, or something?
actually, i have no idea what they're doing in there. Their way of evaluating the integral is completely flying over my head
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Should this problem have two solutions or just one?
They only advise the above x = 30° + n * 120° is the answer
But shouldn't we apply both identities?
It's the fact that the basic angle just happens to be 90
And 180-90=90
So that solution just happens to be included in the given solution
Oic, I mathed more and see that - is x = 30° + n * 120° then considered the better representative answer over x = n * 60° - 30°?
I don't think the other answer works
Try just 0*60-30=-30deg as a test case
How'd you get that one
Oh so are we trying to find the best expressions where n = 0+ fits within the interval?
Yea
Alright if you're done you can close the post
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If There exists a $c \in \R$ such that $a<c<b$ for all $a \in A, b \in B$ then $sup(A) < inf(B)$.
\
I'd try a proof by contrapositive. If $\sup(A) \geq inf(B) $, then there exists $a \in aA, b \in B$, suhc that $a \geq c \geq b ; \forall c \in \R$
ƒ(Why am. I here)=I don't Know
Does this sound right so far
no, not the proof, the contrapositive so far
logically
you didnt negate correctly
if that is your question
$\exists c\in\bR: (\forall a\in A: a<c)\land (\forall b\in B: c<b)$
Denascite
thats the statement you have to negate
So the negation would be $\forall c \in \R : ( \exists a \in A : a \geq c) \lor ( \exists b \in B : c \geq b)$
ƒ(Why am. I here)=I don't Know
If $sup(A) \geq inf(B)$, then $\forall c \in \R : ( \exists a \in A : a \geq c) \lor ( \exists b \in B : c \geq b)$
ƒ(Why am. I here)=I don't Know
This is false consider $A =[0,1] , B= [0.5,1]$. Clearly $\sup(A)= 1$ and $inf(B)=0.5$, This statement is clearly not true for all $c\in \R$
ƒ(Why am. I here)=I don't Know
wait you're showing this is false
yea, I wasn't sure of how to proceed with a direct proof
so I decided to try to prove the contrapositive
I don't think I understand your counterexample still
well its wrong. so that doesnt help
How's it wrong
Yeah, misread the second part
oops
I feel like this is going to be even harder to prove, being a forall statement
hmm
try to find a counterexample for the original statement
shhh
I didn't say a lot
you said whether the statement is true or not
which really is the hard part of true/false questions
I can't talk about the infimum ans supremums of infty
can I
Let $B= [0,1], A=[0.5, 1.5]$
ƒ(Why am. I here)=I don't Know
why
2 is greater than all elements in A and less than all elements in B, so c=2
but sup(A) = inf(B)
Cool
Thanks!
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The uniquness part is confusing me
I'm unable to understand this
is uniquness because composition of functions is always associative
<@&286206848099549185>
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https://prnt.sc/VDBWKoEdn6MC This screen has the question i am a bit confused about, from what I have done so far I am confident in a-c but for d/e i am not 100% certain my answer is right. I got part d as 0.00000054842, and for part e i believe this is just ^3 since there are 3 independent starting points
Please don't occupy multiple help channels.
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How can I resolve this ? I have no idea and I need it. Using guides and AI doesnt help me
It's maybe too easy for you but I dont understand anything
If you just need to solve for z, then a first step is typically to clear all of the fractions. You can multiply both sides of the equation by 10(z+2)(z-4) to do this.
Bring the variables to the LHS and numbers to the RHS
Firstly, make the two fractions into a single one on the L.H.S. For that, you need to take a number of both (z+2) and 10. So you shall just multiply them out. Now adjust the numerators accordingly. Now, use the fact that: if a/b = c/d, then ad = bc
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That’s a solution
Ok
Thank you king
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Ty all
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factorise fully (x^2-x-6)(x^2+3x-4)+24
well first expand to see if the 24 can be factorise once its added to the other constants
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We haven’t really learnt about factorising x^4 and other stuff like that
if youve never done a quartic does your teacher just want you to ignore the +24?
if you dont factorise from a qaurtic
the furthest you can get is
$(x-3)(x+2)(x+4)(x-1) + 24$
Nyxzore
are you supposed to use vieta's formula
I’m not too sure
this is the only thing i see working
i tried expanding it and i got x4+2x3−13x2−14x+48
but im not too sure how to factrosie
use law of natural roots
Sry I’m a bit unfamiliar with this
so some small negative integer should work
and probably also small positive number too
How do we factorise this tho?
find two roots using ^ then polynomial/synthetic division it out then quadratic formula the rest
The idea is that if you plug f(Z) into a function f where Z is an integer if f(Z)=0 then x-Z is a factor
should take you all of 2 minutes to do this
and this
@fierce canyon Has your question been resolved?
<@&286206848099549185> im still rlly stuck
why
i dont understand what to do
.
you said that's where you are almost an hour ago
did you do this yet
plug in x=-1,-2,-3
you didnt really explain much to me
what am i meant to find by plugging in
because he explained it here
there shouldn't need to repeat something already explained when you can just scroll up and read
i didnt really understand what he meant
.............
do this and it'll give you one of the factors
now you have 2 factors
you're at this step now
how would we do that step?
.......
This video tutorial explains how to perform long division of polynomials with remainder and with missing terms.
Algebra - Free Formula Sheets: https://bit.ly/3CBeZMY
Algebra Final Exam Review:
https://www.youtube.com/watch?v=U0Y8nSmEpNM
Introduction to Polynomials:
https:...
did you find your two factors? because you can't do the division until you figure them out
scroll down to see a higher order one https://www.mathsisfun.com/algebra/polynomials-division-long.html
process is the same
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How to find integral on 5)
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hello
i dont think i have question yet
but pls lemme stay in the channel
i got absolutely DESTROYED in my complex analysis exam
took a massive day off for break
but im feeling so defeated and so unmotivated
staying here will keep me accountable
also like again all my friends are getting internships i havent heard back from anything im feeling so worthless rn
#therapy
like absolute sht
Rip
yup yup
If only that was a real channel
Bro needs to seek professional counselling ong
frfr
i got a massive cup of coffee and like nice candles and some chocolate i still feel horriblle
been on my phone for the whole day ngl
its bad
Melt the chocolate into the coffee
making it worse
It's like a ice bath
just exercise bruh
bruh too late now gyms closed and its so cold
yea😔 i just feel so uncapable of anything
because theres nothing to show for it
and social media is bad like rlly bad
Turn the device off and do something to get the blood flowing
its making me want to take an "easier route"
i need to just stop
and start studying for my next exam cause all im doing is complaining
i just need a good cry
whats wrong wme😭
true
engineering
which is why Im gonna start studying now
i'll have questions fs
for this question, we learnt to guess particular solutions (in this case a polynomial, A/x) but the method only works if its constant coefficients in front of y'', y', and y
so what should you do when theres polynomials in front of ys
oh nvm
question only asks for the particular sol, so you dont need the homogenous part
so not the c1y1+c2y2 part
try A/x anyway @obtuse totem
yup! I got it
@obtuse totem Has your question been resolved?
@obtuse totem Has your question been resolved?
not sure how they simplified it lol
oh wait
im good
everything was good until the integral😭
i keep making these mistakes
you know, if I actually get my degree,
that would be the most insane thing ever
C's get degrees is my motto
facts😤
i may be stupid but im still trekking along🤩
you know what maybee i take a break and do more questions later
thank you for tuning into my beauuutiful life story byeeeeeeeee
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Let $P(x) = x^3 - 2x^2 + 3x - 6$. Find the polynomial $Q \in \mathbb{R}[x]$ of minimal degree such that the polynomial $H = P \cdot Q$ has one triple root and two double roots, and $H(-1) = 27$.
938c2cc0dcc05f2b68c4287040cfcf71
What are the roots of P(x) ?
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<@&268886789983436800>
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then youre violating discord's tos bro
Ty
ok bye then
💣
danko
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need help with this:
Prove
Q(k): C¹ₖ₋₁/(k-1)-C²ₖ₋₁/(k-2)+C³ₖ₋₁/(k-3)+...+(-1)ᵏ⁻²⋅Cᵏ⁻¹ₖ₋₁/[k-(k-1)]+(-1)ᵏ⁻¹⋅Cᵏₖ/k=1/k
which can also be written as
1-(k-1)/2!+(k-1)(k-2)/3!-(k-1)(k-2)(k-3)/4!+...+(-1)ᵏ⁻²+(-1)ᵏ⁻¹⋅1/k=1/k
Q(2):1-1/2=1/2 true
Q(3):1-2/2!+1/3=1-1+1/3=1/3 true
Q(4):1-3/2!+3⋅2/3!-1/4=1-3/2+6/6-1/4=2/2-3/2+(1-1/4)=-1/2+3/4=-2/4+3/4=1/4 true
No idea how to prove Q(k-1)⇒Q(k).
Q(k-1): 1-(k-2)/2!+(k-2)(k-3)/3!-(k-2)(k-3)(k-4)/4!+...+(-1)ᵏ⁻³+(-1)ᵏ⁻²⋅1/(k-1)=1/(k-1)
Q(k): 1-(k-1)/2!+(k-1)(k-2)/3!-(k-1)(k-2)(k-3)/4!+...+(-1)ᵏ⁻²+(-1)ᵏ⁻¹⋅1/k=1/k
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Let $P(x) = x^3 - 2x^2 + 3x - 6$. Find the polynomial $Q \in \mathbb{R}[x]$ of minimal degree such that the polynomial $H = P \cdot Q$ has one triple root and two double roots, and $H(-1) = 27$.
938c2cc0dcc05f2b68c4287040cfcf71
@tidal turret Has your question been resolved?
@tidal turret Has your question been resolved?
@tidal turret Has your question been resolved?
@tidal turret factor P(x) first
how
we dont know any roots of P(x)
ah, you mean use rational root theorem?
dont tell me its rational root theorem
i am just giving you ideas, but 2 is a trivial root
so apply euclidean division, P(x) by x-2
and you get the rest of the factors
so already you have 2, and have options to turn 2 into a triple or double root based on your choice of Q
just plug it in man, its a small number that happens to verify that its a root
?
2^3 - 2x2^2 + 2x3 - 6
how did you got it
its not important, you are distracting yourself from the question
but if you really insist:
x3-2x2+3x-6
x2(x-2)+3(x-2)
(x-2)(x2+3)
happy?
@tidal turret
I guess I am happy
$\polylongdiv{x^3 - 2x^2 + 3x -6}{x-2}$
938c2cc0dcc05f2b68c4287040cfcf71
now the next step is to calculate P(-1)
we get that P(-1)= -12
-1 CANT be a root for Q(x) because that would mean H(-1)=0
,calc (-1)^3 -2(-1)^2 + 3(-1) - 6
Result:
-12
so you have to construct Q(x) so that Q(-1)= -27/12 , Q(2)=0 and a root "a" of your choice is triple
we have that Q(x)=(x-2)Q' with Q'(x)=k(x-a)^3
what does Q' denote? the first derivative of Q(x)
no, just a factor of Q
it will be the factor with a triple root
H(-1)=P(-1)Q(-1)
27=-12(-3)Q'(-1)
27/36=Q'(-1)
we now found a condition on Q'
k(x-a)^3 = 27/36 = 3/4 x=-1
we have that?
by construction
how in the world
just re-read my messages
you have problems following, let me get a paper
but the reason is simple
H needs to have a double root and a triple root
P already has a root which is 2
why is 2 a root for Q
Q needs to be the smallest degree possible, so its in our interest to construct Q so that 2 is also a root
we want 2 to become the double root OR triple root
i chose for 2 to be the double root
therefore we get Q(x)=(x-2)Q'(x)
with Q' being a certain polynomial that has a triple root, since thats the goal
do you follow?
wait a second, H = P.Q has to have a triple root and two double roots
how is Q related to the double roots
we found P has a root at x = 2
oh two double roots, i have misread, well nothing changes anyways
Q needs to have x = 2
gimme a second
because H needs to be of a minimal degree
,w x^2 +3 =0
they are complex solutions
P has one real root and two complex
i dont know if the question imposes for them to be real or not
is there any other context provided?
in order for Q to be minimal polynomial we repeat the root of x = 2 for Q
since H = P.Q has a triple root and two double roots
we can repeat the complex roots but is easier if we repeat x = 2
actually it would be advantageous to repeat the complex roots
because that already gives us two double roots
lets repeat the complex roots then
alright then
,w x^2 +3 =0
this means
Q(x)=k(x-2)^2(x^2+3) = k(x-2)P(x)
we only need to find k for the condition on H
H(-1)=P(-1)Q(-1)
27= k(-3)P(-1)P(-1)
27=k(-3)(-12)(-12) blablabla
k=-27/432
k=-9/144
,w expand (x-isqrt(3))(x+isqrt(3))
no need to manipulate the complex roots
Result:
-432
,calc 27/432
Result:
0.0625
yea thats 1/16
2 is the triple root
and the two complex roots from P are the two double roots
for Q
,w expand (x-2)(x^2+3)
lmao
I understood, but It wasn't easy
it comes with time
dont think in terms of theorems, its more liberating, you should only draw them last
sometimes solutions are just infront of you
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i dont even know where to begin with this
i looked it up and it said smth abt Ricatti equations - but this is meant to be an interview problem so
what's going on here
I am not too good at these; maybe this observation helps: sometimes, when you have dy/dx = y^2, the solution uses the property of a/x acting similarly when differentiated and squared.
oh i see a bit?
although I am not 100% it's useful here.
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$$I=\int^{\pi}_{0}\dfrac{x|\sin 2x|}{3+\sin^2 x},dx.$$
Amadeus
how do you even approach this
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substitution u=pi-x would be good
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is this integral converge conditionally? and if does how to prove it?
it does converge, you can check this by splitting up your integral in 3 parts
1 from 0 to epsilon
1 from epsilon to N, where N is a big finite number
1 from N to infty
for very small x the sqrt(x) term will dominate, and for very large x the x term will dominate in the denominator
@young pelican Has your question been resolved?
to prove it formaly should i use dirichlet's test or something else?
the dirichlet's test is perfect for this, for example one can show that
$\int_1^{\infty} \frac{\sin(x)}{x} ,dx$ is convergent using the Dirichlet test, which is similar to your problem.
tobi
ok ty
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Martha arranged books on two shelves with the same internal dimensions. All the books were the same size. She filled the first shelf (I) completely with 12 books. On the second shelf (II) she decided to arrange the books side by side across the entire width of the shelf so that there was free space above them, as shown in the drawing.
Note: the drawing shows the first shelf completely filled with books (I) and the second shelf partially filled with books (II).
How many books at most could Martha fit on the second shelf (II) with the arrangement shown?
A) 7
B) 8
C) 10
D) 11
6b = 21 cm
b = 21/6
b = 3,5 cm
28/3,5 = 8
So she can fit 8 books?
B)?
<@&286206848099549185>
seems logically sound
Hi
Hola
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answer is 152 but how teacher didnb give explanation
since AB is parallel to CD, angle BDE is 76
mhm
x is angle d + b
because ABD and BDE are alternate interior angles
and angle BDE is equal to angle DBE since triangle DBE is isosceles
so angle BED is 180-76-76=28
x is 180-BED=180-28
no perm moment
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One gear turns $33\frac{1}{3}$ times in a minute. Another gear turns 45 times in a minute. Initially, a mark on each gear is pointing due north. After how many seconds will the two gears next have both their marks pointing due north?
938c2cc0dcc05f2b68c4287040cfcf71
is lcm lcd exercise not related to physics btw
but if you want we can look for angular velocity
i know but i had a question like this in my physics course and i found it easier with the angular velocity, let me try without it tho
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
Mb I mean
alright so after finding w, you can do is 2pi* n1 = w1* t and 2pi* n2 = w2*t
n1 and n2 are just any natural numbers
You have the functions
(100/3)*t and 45t
And we're trying to find the t when both functions are whole numbers
I need more handhold
how do I find the w velocity
how do I find the t such that both functions are whole
do you know what w is
I feel like finding w is MASSIVELY overcomplicating an LCM problem...
Find out how many seconds it takes for each gear to make a full revolution, and find the lcm of those two numbers and you're done
100/3 times/min means it spins 600/3 = 200 times/sec, or it takes 1/200 seconds to spin once. the other is 45*60 = 2700times/min, or it takes 1/2700 seconds to spin once. just find lcm there and you're done
@tidal turret Has your question been resolved?
i took this approach too
you can factor 100 and factor 45
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can someone please explain why (B) is wrong
you only know that f(2) = 6
you don't know anything about f(2 * 2) = f(4)
f(4) could be anything!
isn't there a limit property where you can pull out the constant
you've confused $f(2x)$ with $2 f(x)$
south
like if I know that $f(x) = 6$, then $3f(x) = 18$
that's where this limit property comes from
south
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Can someone explain how the correct answer (B) was found because I got (A) and I don't know how to do it... https://www.desmos.com/calculator/0wr3u3actd <- desmos with relevant functions
you just set $\frac{d}{dt} (f(t) - g(t)) = f'(t) - g'(t) = 0$
south
find the value of t
no need to sub the critical value of t back into f(t) - g(t), cause that would give you the max number of people
besides you don't know what f(t) and g(t) are without integrating
yes click on your graph to find the zero of the function
it is indeed 7.888
there is another one at 10.974 yes but you can look at the graph
only t = 7.888 goes from positive derivative to negative derivative
so increasing then decreasing
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Show that if $a,b \in \Q$, then $a+b$ and $ab$ are also rational.
\
Proof: Suppose $ab$ is not rational. Let their product be $c$. We then have $ab = c$, or equivalently $a= \frac{c}{b}; b\neq 0$. However, a being rational is the quotient of two rationals, this contradicts that. Therefore $c$ cannot be irrational.
ƒ(Why am. I here)=I don't Know
what is the question here?
oh
i think it could be more rigorous
Hmm, how?
but intuitively it makes sense
How
you're assuming an irrational over a rational is irrational
yeah that
c is not irrational
He assumed c is irrational
yes
And cant be expressed as real / real
oh
Yes i think
I see the problem
i don't see anywhere he showed c is rational
Yeah this is just a constructive proof, you didn't use the assumption that c is irrational anywhere
i agree a direct proof will work
Hmm, okay
Ah i got confused
let me think
you should use the definition of rational
You're also assuming b != 0 which isn't really necessary
yea
if a is rational then a = p/q where p, q = ___?
W
I'm just using the fact that every rational is the quotient of two rationals by defn, no?
@twilit field Let a = x/y and b = m/n where x, y, m, n belongs to Z
it can be expressed as a quotient of two integers
but it can also be expressed other ways
for example, as an irrational over an irrational
for example, 1/2 is rational but it's equal to sqrt(2)/(2sqrt2)
I think That's overkill, for I don't know anything about xm/yn
no that's right
you might need to prove the lemma if gcd(p, q) = 1 then gcd(p^n, q^n) = 1
you know xm is an integer and you know yn is an integer
so I assume closure under multiplication of integers
yes
p,q \in Z
$
we would normally build integers first before building rationals
so
we can assume integer properties
i mean in theory, anyway
Why?
How did your book define the rationals
A rational is any number that can be expressed in the form p/q , where p,q are integers
So what does division mean here
hm
p, q are coprime i.e gcd(p, q) = 1
Let $a= \frac{p}{q}, p,q \in \Z$, $b= \frac{m}{n}; m,n \in \Z$
\
$\frac{p}{q} \frac{m}{n} = \frac{pm}{qn} =c \implies c \in \Q$
ƒ(Why am. I here)=I don't Know
multiplication by $q^{-1}$, right
ƒ(Why am. I here)=I don't Know
looks reasonable
Not necessarily
Yes
yeah get a common denominator etc.
But you don't know how multiplication works yet
$\frac{p}{q} + \frac{m}{n} = \frac{pn+qm}{nq} = c$ again
ƒ(Why am. I here)=I don't Know
You should probably prove this
are you talking about multiplication in Q or in Z?
I think in my book we formally construct the reals in the 8th chapter
You're assuming you know how multiplication and addition works in the rationals
yeah, section 8.6 is a construction of R from Q
But that doesn't constitute a proof I think
yeah, that should also be a matter of definitions, right?
Why?
shouldn't there be a definition of multiplication in Q that he can use?
pq^{-1}mn^{-1}=pmq^{-1}n^{-1}
Yeah it depends on how things are defined
that does seem more rigorous
hmm
what are we solving?
We're done, I think
But this
so proving a+b and ab are ratrional?
ye
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