#help-49
1 messages · Page 197 of 1
not piecewise?
different definitions of the function at different domains
Wait, sorry could you clarify more by this?
|x| has a turning point at x = 0 and yet it’s derivative is not zero at x = 0 (since it isn’t even defined at x = 0)
yeah piecewise lol just looked it up, wasnt taught that word
derivative is mod(x)/x, not defined at x=0
Ohhhh ok. Ahhhhhh, I was meant to say turning point of a differentiable function. I think that makes a difference
yea that’s different
I mean it can at most be n-1, that’s true. But say for example we have a fourth degree polynomial. It cannot have two turning points im pretty sure, neither can it have 0 turning points, but it can have 1 or 3 turning points
we have to take the maximum possible case though, so picking a specific example won't lead us to the result
Sorry, could you clarify?
I’m sorry if I’m acting stupid, I’m still in pre-uni
we have to take the maximum possible turning points
wait i misread your statement i thought you were saying that a fourth degree polynomial cannot have n-1 as its maximum possible turning points
i apologise
so it depends on if n is even or odd then
Yes, that’s what I said before (in original message)
I’m sorry if I worded my question badly. It seems that there are a lot of misunderstandings happening
no it was my mistake not yours lol
about the proof for p(x) and ax^n
i dont know if there are other methods but i was taught this way:
take the limit of p(x)/ ax^n
it will come out to be 1
so for very high degree polynomials p(x) is approximately ax^n
Ohh ok, makes sense
so you just need to show that the number of zeros of odd multiplicity of p’ are even/odd based on the parity of n
because that’s where the turning points occur
Oh ok
Okay I think I’m good now
Thanks everyone!
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you got your answer?
I think so
nice
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Find value of r so that this function has limit in x = -2
there's no need for finding the limit of the function for which x<-2
just the first two will suffice
put x= -2 in the second function to get your' reqd limit's answer
yeah since if you're taking limits the function is continuous
so it doesn't matter which one you solve the 2nd or 3rd
is that understandable?
yep
now take the limit of the first function as x approaches -2
(that limit is -3)
so you'll find r
and just solve for r
yep
r = 1
you want me to check?
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Can someone please help me with this question? Thanks
i just saw that message of yours lmao, why did you instantly close it after explaining
well the hint looks like it could be useful have you tried that yet
yeah i did
what'd you get
can i send a photo?
yeah
well i'm not too familiar with what the conventional approach would be for these types of questions but if it were me i would do something like
first move from A to all adjacentR's
then move from R to adjacent C's
then from C to adjacent H's
okay here's the photo
please ask me if you have any questions (ik the handwriting is not the best)
you did the other letters as well?
yeah i thought that's what you were supposed to do?
no im asking if you did the same thing with A and C
well your working seems right
for R
it's just a lot of working, nothing else to it just do the same thing for all of them
could you please clarify what "all of them" is
all the other letters i already did tho
well then just add all the cases you got ARCH in
but there's only 1 option for A so why would that matter
how is there only one?
you can move to both right and down
oh you mean as in there is only one A
yeah
well yeah but you still need to make the cases for it
like all the different ways it can go to a R
oh ok
I got $\left(3\cdot2\cdot2\right)+\left(3\cdot2\cdot3\right)+\left(3\cdot5\cdot2\right)+\left(3\cdot5\cdot3\right)+\left(3\cdot5\cdot5\right)+\left(3\cdot5\cdot3\right)+\left(3\cdot5\cdot2\right)+\left(3\cdot2\cdot2\right)+\left(3\cdot2\cdot3\right)$
RamenNoodleMan21
i didnt calculate but that number just seems too big at first glance itself
well i tried to include every possible choice
yeah
im getting 21
holdup sending my work
Idk if its correct theres so many cases
only the C to H displacements matter for our final result btw
no 21 is incorrect too
it's too small
idk then man you should ask someone else perhaps
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it's not that far off
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ok this is correct right?
i just wanted to clarify that when it says put in a+bi format this still counts even though its negative
looks correct
b is just gonna be negative, no big worries
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can someone check my work under the line?
this is the elipse equation im solving for
i didnt end up using the first equaition under the line sorry
im not sure where the /13 and /81.25 comes from, but without those its correct
mhm
so wait
then you have to reduce it so they both get put over 325
and 25/325=1/13
and 4/325 = 1/81.25
Shouldn’t there be -225 in RHS ? before dividing
what do you mean?
oh wait youre totally right
Most of these conic sections problems I saw have natural numbers so felt something is messed up
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my knowledge is very limited on this topic and i dont know alot of information.. how do i do these and what formulas do i use if i even use any
Do you know about the unit circle?
Do you know how to express tan in terms of sin and cos?
yes
how would that help with these tho?
understanding what cos and sin represent graphically can help you better understand how to figure these problems out. I wouldn't recommend drawing the unit circle and trying to re-derive them, but you should understand it to the point where you can go about doing something like that
this identity is useful because you're given a theta for problem 8
now, the problem reduces to determining the value of $\frac{\sin\theta}{\cos\theta}$
00100000

i mean i have a unit circle drawn on a seperate sheet of paper with all the information written on it, which helps alot
i get that, but how would i find sin theta or cos theta?
note that $-\frac{5\pi}{6}=2\pi-\frac{5\pi}{6}=\frac{7\pi}{6}$. This is because on a unit circle, the - represents the angle below $y=0$, which can be expressed by going ccw until your positive angle reaches that measure
00100000
excellent
wait why is texit she/her now lmao
anyways
you can take your time lol
isnt this part all we need
yeah, you could just say "plug that into your calculator" I suppose lol
no
but I'm gonna need you to use some of your imagination now @delicate flower
tan 7pi/6 is tan( pi + pi/6)
For better understanding I would recommend you to read on "Rotations & Reflections of Angles".
wait a sec, is tan linear like that!?
well, not linear but
👍
well anyways
periodic
oh, it's not additivity. I see
if tan was linear, all of math would change
yes I didn't think it would be linear lol
so just 1/root 3
this works perfectly well I guess. I was gonna go for the intuition sort of route
yeh sorry i forgot to put the brackets lol
of thinking of moving the unit radius that angle
and then dropping the line down to form a triangle
and then noticing that it's a 30-60-90 triangle
visualising is better with the unit circle
and then getting the identities from that
but for quick math ASTC works best
and then using the tan identity
the quotient identity
All- sin- tan- cos btw incase someones not familiar with the fullform
yep
let me know if you're interested in me continuing, or if @desert siren's answer suffices for what you need it for
i got it infront if me
i understand the
Negative numbers
and how they work
im gonna reread what was said again and try to solve it now, but thank you both alot
of course. glad to be of help. good luck with the problem
i got my triangle, how do i know how to find sin and cos tho
are you aware of the 30-60-90 triangle ratios?
if not, here's how you can derive it. First, construct and equilateral triangle of side length 2, and then draw an altitude of it
the two halves should be congruent by AAS (shared side, right angle, 60 degree angle)
then, the altitude bisects the side it connects to since the two segments it is bisected into are congruent (since they are corresponding parts of congruent triangles)
(i edited my message to use side length 2 for convenience)
then, the bisected segments are of length 1
now, since it is a right triangle, apply pythagorean theorem
yep exactly
so now, your hypoteneuse needs to be 1, right?
oh correct
you should be able to proceed from there on your own I think
yes, it is a radius of the unit circle centered at the origin.
so switch 1 and 2?
the pythagorean theorem
definitely don't switch them
I'm suggesting that you divide both by 2, so that you can preserve the fact that your hypoteneuse should always be of length 1
ohh
you can disregard this, because it was me telling you how you could reason that the 30-60-90 identity is true
well what im stuck on is how to find sin theta with the triangle
well, this goes back to what sin is supposed to represent graphically
it will represent the signed size of the vertical part of the triangle you constructed
(with hypoteneuse of length 1)
it's signed because it needs to be negative if you're in a quadrant where y is negative
quad 3 is where only tan is positive so ya itd be negative
yes, since sin and cos are both negative in that quadrant, right?
correct
@delicate flower Has your question been resolved?
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-1,-w,-w^2 are singularities but 0 is also singularities if yes then why? Because of e^(1/z)??
presumably w = e^{2πi/3}
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you are using l-hopital right?
why didnt you differentiate numerator but not denominator
Yes
Where am I doing mistake?
I dont understand how you went from the 2nd last step to the last one could you elaborate
i expanded cosx and (1+a/x)^(1/2)
Hm i forgot what the expansion of (1+a/x) sqrt would be, but from the second last step you can just cut out x^2
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Yw
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can you find f^{-1}
Is this wrong?
i am stuck on the finding roots step
Should I square it or not?
Or the condition x>=-1 makes any effect?
yes, unjustified involvement of complex
you are working with real only
So how will I solve?
(x+1)^2-√(x+1)=0
Where is it mentioned?
The condition x>=-1
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How do I find two sequence functions that converge uniformly on a segment I, and their product does not converge uniformly on I ?
@graceful ferry Has your question been resolved?
@graceful ferry show me what youve tried
I had 0 intuition on what the sequence function would look like so I just took a function that isn't uniformly convergent which f_n(x)=x^n on [0,1] and tried to get two sequence functions from it but every two I thought of were also not uniformly convergent on the segment
id tell you think of a seqeunce function like any simple sequence x_n (for simplicity) where x_n which is uniformly convergent on I, now do you know the definition of uniform convergence?
yes I do
use that definition to find and proove that those two sequences are uniformly convergent in that interval I
What two sequences
I need to find them in order to prove it
I can't find any that are uniformly convergent and idk how
(Where their product is not a uniformly convergent sequence funciton)
can you come up with anyy example of a congergent sequence?
f_n(x)=x^n on segment (0,1)
well x^n converges but does not converge UNIFORMLY in the segment you can check using the definition
also sorry for late reply im at my work now
IIt does uniformly on the Open segment (0,1)
But that doesn't matter this isn't my question
I can show u proof
show me i might as well be wrong
prograce
This converges uniformly on all R
okay i cannot check rn myself but can you check if you can confine it to a segment like [0,1]
also check another sequence, it could itself be the second sequence, where the multiplaction just squares it
Ok
The sequence squared is still uniformly convergent
on tip of my tounge one uniformly convergengt function i cant think of is 1/n
whats a segment, a bounded interval?
i think Rudin uses that term to mean somethinh like that
Just any domain idk I used google translate for the word
ah okay
Their product is still uniformly convergent
!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
yeah 1/n^2 is convergent
קטע does mean segment but lmc if it means interval in math
I feel like there's no such functions
i think it does
are there any convergent sequences not uniformly convergent that you know of?
Yes x^n on [0,1]
so factor that into two uniformly convergent sequences
maybe the answer will be more obvious if you consider x^{n+1} instead?
ah doesnt quite work
but i think this is the approach
lets try an unbounded interval
more room for pathological stuff
something that converges but not unifornly on all of [0,infty) let's say
$f_n(x) = \frac{nx}{1+n^{2}x^{2}}$
prograce
this doesn't converge uniformly on all R
Maybe I can factor out two uniformly convergent functions from it
ah got one
found an example
think simpler
Wait I found two functions
f(x)=x $g(x)= \frac{n}{1+n^2x^2}$ but interval has to be $[1, \infty)$ to prove g(x) converges uniformly which then works i think
prograce
יופי
(f_n(x))=(x,x,x,x,...) to make it a sequence of course
Oh yes
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Integration (sinx+cosx)
is that what we need to find
I want to find area
ok
Do you know how to integrate (find antiderivatives)?
and what are you struggling with
This is not where i am stucked
As you can see the limits
What will be the limits?
And how do we integrate
oh
So what do you need help with
Each integration needs limits
You want an indefinite integral??
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.reopen
✅
@rancid vigil
You wanna say anything or help
How will you find the area of given graph and axis?
,w 0 to π integration sinx+cosx
.close
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I am inspired
To do part i), do we just use integration by parts?
$\begin{matrix}\quad&\mathrm{D}&\mathrm{I}\+&\log(1-t)&\frac{\log(1-t)}{t}\-&\frac1{t-1}&\mathrm{Li}_2(t)\end{matrix}$
;(
overguting
any latest llm can solve it, dont waste time on it
I'm here to learn!
check what you need to proof , and tally the first part
So log^2
its there as it is
My brain is not braining
and new term log x
YEAHH
lemme cook
add ELI5 to your prompt.
!nogpt
Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).
bro was enlightened by flux
$\begin{matrix}\quad&\mathrm{D}&\mathrm{I}\+&\log^2(1-t)&\frac1t\-&\frac{2\log(1-t)}{t-1}&\log(t)\end{matrix}$
I'm not going to use AI lol
lemme ELY5 , this is a grownup table 😍, if you wanna learn you can join
if it isn't clear enough already
Indeed 
;(
Ok so I have to make ln=log for this
ugh
OH FUCK THIS INTEGRAL?!
NOOOOOOOOO
Bruh I don't like this integral but whatever
$\log(t)\log^2(1-t)\bigg\vert_0^x+\int_0^x\frac{2\log(1-t)\log(t)}{1-t}dt$
;(
$I=\log(x)\log^2(1-x)+\int_0^x\frac{2\log(1-t)\log(t)}{1-t}dt$
;(
(doing great)
How else am I supposed to do it without paper
💀
valid point
Hint 2.4
💀
w hint
Now what to choose
differentiate log(1-t)log(t)?
$\begin{matrix}\quad&\mathrm{D}&\mathrm{I}\+&\log(1-t)\log(t)&\frac1{1-t}\-&\frac{\log(1-t)}{t}+\frac{\log(t)}{t-1}&-\log(1-t)\end{matrix}$
;(
why is the group named help-49 like it reminds you to get 50 on that math test and not help-69
!redir
This channel is only for on-topic discussion. Please take casual conversation to #discussion or #chill.
ok
Ok so that looks wrong
I mean I guess it works...
Maybe it's meant to be
Oh I screwed up
$I=\log(x)\log^2(1-x)+2\int_0^x\frac{\log(1-t)\log(t)}{1-t}dt$
Ok so I screwed up somewhere?!?!?!?!
try and create a dilog
In the IBP?
yes
uh
specifically the du
$\int\frac{\log(1-x)}{x}dx=\mathrm{Li}_2(x)+C$?
;(
works
.
Are we deadass
Aight so I was just being blind...
$\begin{matrix}\quad&\mathrm{D}&\mathrm{I}\+&\log(1-t)&\frac{\log(t)}{1-t}\-&\frac1{t-1}&\mathrm{Li}_2(1-t)\end{matrix}$
;(
By the way do you like this integration by parts things that I am doing
with the LaTeX environment
ok I'm cooking
$I=\log^2(1-x)\log(x)+2\qty(\mathrm{Li}_2(1-t)\log(1-t)\bigg\vert_0^x+\int_0^x\frac{\mathrm{Li}_2(1-t)}{1-t}dt)$
.
;(
I dont wanna \newcommand bro

whoa!
I think I see the simplification
$\log^2(1-x)\log(x)+2\mathrm{Li}_2(1-x)\log(1-x)-2\int_1^{1-x}\frac{\mathrm{Li}_2(u)}{u}du$
;(
🙏
This is glorious
$\log^2(1-x)\log(x)+2\mathrm{Li}_2(1-x)\log(1-x)-2\qty(\int_0^{1-x}\frac{\mathrm{Li}_2(u)}{u}du-\int_0^1\frac{\mathrm{Li}_2(u)}{u}du)$
;(
GLORIOUS I SAY
🗣️
$\log^2(1-x)\log(x)+2\mathrm{Li}_2(1-x)\log(1-x)-2\mathrm{Li}_3(1-x)+2\zeta(3)$ FROM OUR PREVIOUS DISCUSSION
;(
PROOF BY FLUX BEING A NICE GUY
🗣️
@long dagger 
Thank you bro
The next question looks cused
I'm gonna take a break
.close
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I was just confused about the purpose of this question for my linear algebra class.
I didn't totally understand what I was being asked to do, but I feel like I already knew a b and c would all equal 0 once I got the matrix to rref. I still don't really understand what I was doing tbh
it's well known that a polynomial cant have more roots than its degree, but this is showing it to you from a linear algebra perspective
tells you parabolas don't intersect the x-axis more than twice unless it's the 0 parabola
you can approach that theorem from different viewpoints
it's making you use linear algebra tools to view a problem as a linear algebra problem, even if you know the solution from somewhere else
you learned about bases yet?
Yeah this is like
anyway, you know that two polynomials in the same variable are identical if and only if the coefficients are equal , right?
Yeah
this can be written in linear algebra language in a very deep and profound way that implies that a polynomial cant have more roots than its degree
The space of all polynomials with complex coefficients in a variable t has a basis:
${1,t,t^2, t^3, t^4, \cdots}$
gfauxpas
try proving that two polynomials are equal iff they have the same coefficients by treating them as vectors written with this basis
fun exercise
... if youre looking for extra homework :P
We haven’t talked about vectors yet, we started with solving systems with matrices
and Gaussian elimination
ah okay
but I’ll come back to this problem like next week I think
or two weeks
It does make sense now though, thank you 🙂
@main nebula Has your question been resolved?
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anyone know the best way to solve this type of quesitons
slope field must provide tangent lines everywhere along the graph of a solution
so how would i go about solving it
plot solution and see which field provides tangent lines
Tbh, you can kinda just see which one is correct
You should just know that it’s a semicircle with radius 2, centre at the origin
Where y>0
how would i know that
x^2+y^2=r^2?
yes
Yeah
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can someone help with this im confused on the part it says its initally 300 pop
but the max capacity is 500 so wouldnt the rate of change be fastest at 250?\
For part b?
yes
i think thats the answer but im confused on the inital population
how cn there be 250 pop when inital is 300
Are we sure that 250/4 is the answer it wants?
no thats not the answer im pretty sure the answer si 250^2(0.001)
That's the same thing
Assuming 250/4 is correct, it just says "the growth rate will never exceed", so I guess we're just putting an upper bound on the growth rate, even if it will never reach it. So the initial population doesn't matter.
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shouldnt we choose a person for the first seat in k ways?
cuz there are k seats in total
and then when one person is seated the no of seats for the next n should be k-1
so shouldnt the answer be k(k-1)..(k-n+1)?
no you have it backwards
we go down the seats in order and for each seat we look at how many people can sit in it
when we are on the first seat nobody has been seated yet so any of our n people can sit there
n is the number of ppl
ah
can u make the last one being (n-k+1) more intuitive?
like i get it but its not really intuitive
when we're filling the last of the k chairs
the remaining k-1 chairs are already taken
thus there are n-(k-1) people remaining at that stage
in how many ways would the k-3, k-2, k-1th chairs will be taken
i can't parse that
do you mean to ask how many options we would have to fill the (k-3)rd, (k-2)nd and (k-1)st chairs?
n-k+4, n-k+3, n-k+2 respectively
i dont understand why these are equal
or multiply the left hand side by (n-k)! and see what happens
@narrow edge Has your question been resolved?
i still dont see it
could u similfy it
n! is the product of all integers from 1 to n
dividing by (n-k)! destroys all the ones from 1 to n-k inclusive
the smallest one left standing is the next one after n-k, which is n-k+1
@narrow edge Has your question been resolved?
ohh so (n-k+1)(n-k+2)...(n-k+k)
i get it
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√(2^x-5^x) domain
Officially karna chahte ho agar toh
2^x-5^x>=0
2^x>=5^x
x(log2/5)>=0
x<=(log(2/5)^0
x<=1
But it doesn't satisfied at x=1
Which step is wrong?
x(log2/5)>=0
x<=(log(2/5)^0
wow you put like 5 newlines between these
anyway this is the wrong step
from log(2/5) * x ≥ 0 you divide by log(2/5) and flip the sign (because log(2/5) is negative)
and you get x ≤ 0
log(2/5) is less than 1 so when i took it to right side inequality reversed no?
less than zero not less than 1.
comparison against 1 has no meaning here
you care about positive vs negative not <1 vs >1
This is also wrong no?
less than 0 is complex
Which we don't care here
So 'wow' to you also you discovered a new hypothesis
no.
you confuse condition on x with condition on log(x).
also you didnt write any base for the logarithm anywhere so i assumed it was either e or 10 and both of these work equally well here we just need to be consistent
Consistent at what point?
Logx when x<0 ?
How can we apply inequalities in complex?
Could you explain this line means please?
consistent means we read your logs as log_e always or as log_10 always but not mix
i meant that when we multiply or divide both sides by a number in an inequality we care about whether this number is positive or negative
but we do not care if it's <1 or >1
in your case this number is log(2/5)
it is not 2/5 it is log(2/5)
log(2/5) is not same number as 2/5
i believe you have mistake even earlier
after 2^x>=5^x you should get
(2/5)^x>=1
so
log_{2/5}((2/5)^x)<=0
x<=0
Yes (log2/5) would be a negative number
So inequality reversed
I got your point and mine too
I was telling about the base yes. Thanks again
And sorry for some silly words in middle of the chat
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F(z)=e^(1/z)
singularity at z=0
so here by laurent expansion
1+1/z+(1/2z^2)+...
here multiply of 1/z is 1?
so is it called residue at x=0 is 1?
It contains infinite isolated singularity so it is essential singularity
Hmm
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how do I check whether the sum $\sum_{n=1}^{\infty}\frac{(n!)^2 \cdot 4^n}{(2n)!}$ converges or not
prograce
I tried ratio test but I got q=1 so it wasn't helpful
How can I possibly find a sum that is bigger than it which is easier to test for converges so I can use comparison test?
Or how do I do it in any way?
you can simplify first by dividing both numerator and denominator by (n!)
then you can do ratio test
To get rid of the denominator ?
the denominator is just (1 * 2 *... * n * n+1 *... *n + n) = n! * (n+1)(n+2)...(n+n)
now youre just left with [(n!) * 4^n ]/ [(n+1)(n+2)...(n+n)]
then you can do ratio test
well thats not the ratio test
no ratio test
he said in the first message that the ratio test was inconclusive though because was equal to 1
do the terms even go to 0
you mean the limit of the sequence as is?
Bro omg mb
,w lim n to infinity ((n!)^2 * 4^n)/((2n)!)
Yeah, and that's why I misunderstood for root test
How would diving numerator and denominator by n! change the outcome I got which is q=1?
ratio test fails? try raabe's test.. raabe's test fails? try logarithmic test. it will work in one of them surely
I didn't learn raabe test or logarithmic test
Not in material of my course
There has to be another way ?
.
this sequence diverges
well as i see here it diverges, so maybe some comparison test
nth term test?
Thta's what im trying to do but idk what to compare it with
Ohh
Ok so it's divergent by no.1
how do u show that the limit diverges tho
My next problem
why did you deleted
@graceful ferry Has your question been resolved?
is it direct comparison?
is fine, we are getting there XD
I have some idea, why not direct compare it with
((n!)^2 . 4^n)/((2n)!) <= ((n!)^2 . 4^n)/(n!)
now the problem is reduced to finding what does this limit approaches to
lim n to infinity of (n! . 4^n)
it approaches infinity
yeah XD
is fine, this one was really fun, also prograce is kind of my discord buddy so i tried extra hard
you had great ideas tho, and was really helpful aswell
Oh nice
That was really simple
nope. the series on the right hand diverges, but it doesn't tell you that the series on left diverges. if you have an <= bn and bn diverges, it doesn't say an diverges. if an >= bn and bn diverges only then can you say an diverges.
we are doing nth term test
What how? Comparison test is : if bn>=an and bn diverges then an also diverges
its actually
[ \frac{(n!)^2 4^n}{(2n)!} \leq \frac{(n!)^2 4^n}{(n)!}]
since $(2n)! \leq n!$
k
so the thing still makes sense
wati
wait a sec
am i high
i am high
ye
u cant use that proof
neh you have it flipped. just think lol a series bigger than your series is diverging it doesn't say shit, if you pick any convergent series there are many divergent series that are greater than the convergent series.
Yes I am reviewing ur right
I can't myself find a comparison, well i would've relied on tests to show the divergence as i have first told you.that usually sets the game.
I would use them too but this is homework I will submit and I cant use tests I didnt learn
They usually teach rabbe and another test but this semester is shortened so we didnt learn them
idk
Real
chat
while trying to find other forms of my combination stuff
finally
my curiosity put to rest
@graceful ferry
Thank you!!
But since it's an approximation can u just substitute it ?
yes for n approaching infinity
Stirling approximation huh. For last measure I will use this but I will still try to think of another way
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How do I calculate $\sum_{n=0}^{\infty}(-1)^n\frac{n^3}{n!}$ ?
prograce
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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
1
Try to write the first 5 terms first to infinity as a sequence
does this look like any series you are familiar with ?
yes and youre gonna need to fiddle around with it a bit
$\sum_{n=0}^{\infty}(-1)^n\frac{x^n}{n!}$
prograce
yes nice
can you think of any operation we could do to this get to get closer to our target series ?
The n^3 bothers me
yeah there is a way to get rid of it
actually i recommend working with just \sum x^n/n! with the eventual goal of evaluating the thing at x=-1
here is something to think about
what if instead of n^3 you had n(n-1)(n-2) in the numerator
what could you do then
no need actually
$\sum_{n=0}^{\infty} \frac{n(n-1)(n-2)}{n!} x^n = \sum_{n=3}^{\infty} \frac{1}{(n-3)!} x^n = x^3 \sum_{n=3}^{\infty} \frac{x^{n-3}}{(n-3)!} = x^3 e^x$
Ann
=(-1)^3e^-1
hold off on the evaluation at x=-1 until everything is actually sorted the way it needs t obe
do you understand the basic idea here
I understand it
that if the numerator cancels nicely with some shit in the denominator to leave a lower factorial,
then you can rewrite things in terms of e^x directly-ish as i showed
Oh but n^3 is not n(n-1)(n-2)
right
Yes
so then you will perhaps want to express n^3 as a linear combination of:
- n(n-1)(n-2)
- n(n-1)
- n
and break the sum into 3 and do the trick on each one
Ok
How do I do that ?
$n^3 = An(n-1)(n-2) + Bn(n-1) + Cn$, solve for the constants $A$, $B$ and $C$
Ann
there is a smarter way to do it if you're up for it
Yes sure
If there's a less work way
n^3 - n(n-1)(n-2) is going to not contain any n^3 term
so the coefficient on n(n-1)(n-2) has to be 1
and now you need to break the rest into a linear combination of n(n-1) and n
Yes
figure out how much this "rest" is
B=3 C=1
ok good
so now you can break the sum up as:
$\sum_{n=0}^{\infty} \frac{n^3}{n!}x^n = \sum_{n=3}^{\infty} \frac{n(n-1)(n-2)}{n!}x^n + 3 \sum_{n=2}^{\infty} \frac{n(n-1)}{n!}x^n + \sum_{n=1}^{\infty} \frac{n}{n!}x^n$
Ann
(also trimming zero-coefficient terms here)
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is the answer A because when u equate lambda and mu it cancels out
ok so you got that the system reduces to one equation that expresses lambda in terms of mu (or vice versa)
yes, that means the two lines are one and the same.
wait they don't intersect if you find a value for lambda/mu and it doesn't work for the third equation right
i think i got that mixed up
if your system ends up inconsistent then yes that means the lines don't interact
but you arrived at no such thing
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Given $f(x,y)=\sqrt{\frac{y^2-1}{x^2+1}}$ I wanna find what shapes there exists between the contour lines of f
prograce
$\sqrt{\frac{y^2-1}{x^2+1}} = c$ \
$\frac{y^2-1}{x^2+1} = c^2$ \
$y^2-1=c^2(x^2+1)$ \
$y^2-c^2x^2=c^2+1$ \
now how do I find what shapes I can have based on the different values of c ?
prograce
Write (y-c x)(y+c x)=c^2+1 and consider the lines y= +-c x
Can you give another tip ?
@graceful ferry Has your question been resolved?
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so is the computer just dumnb
extra 3
hmm?
oh no you did nothing wrong
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for T is injective -> T^m is injective , I was wondering if just saying compositions of injective functions is injective is enough, or if a proof is needed
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guys i gave an extremely difficult questions of Sequence and Series. Q) If (a+1),(b+1),(c+1),(d+1) is in GP then find the value of (b+c+2)^2 = _____ options:- (a) (a+b+2)(b+c+2) (b)(a+b+1)(c+d+1) (c) (b+c+2)(c+d+2)
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Please help me on this question
I think the order of the sequence is ACACACAC
But I don't think there are any other sequences
But idk what to do with the "two seatings" part
<@&286206848099549185>
It means that ABCDEFGH is the same as BCDEFGHA.
That's just the first one rotated, so it's the same.
A1, C1, A2, C2, A3, C3, A4, C4
Yes, that's one possibility.
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A2, C1, A1, C2, A3, C4, A4, C3
No, you want to start the sequence out with the same adult.
This makes it possible to ignore rotations.
Oh so the beginning has to be A1?
Yes. This is because all rotations of a sequence are the same, so you just choose an arbitrary starting point for each sequence.
You could also choose like C3 to start it.
It doesn't matter. You just need to always start with a particular person to handle all rotations of the sequence.
Like ABCDEFGH is the same as DEFGHABC, so you might as well just write it starting with A.
So there are 3!=6 ways to place the A's
Right.
And there is 4!=24 ways to place the C's
Right.
and then we multiply them cause they're independent events
Yes.
oh so the answer is 144 thanks
No problem.
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Please help me on this question