#help-13
1 messages · Page 169 of 1
then i have to consider the case where numerator < 0 and denominator < 0?
but denominator < 0 gives 2^{4-k} < 0 which is never true
made your own life complicated there.
you mean i could just cross multiply?
do you want to know how to do this without headache or do you insist on doing it specifically this way
i would like to know how to do it without headache, but if possible i would like to clarify if i'm approaching this rational inequality right
just for future references
maybe not so much for this question
oh yeah whoops
if i'm dealing with this
would i have to consider the case where denominator = 0
as well as numerator = 0 and then work on that basis?
i'm guessing the non-headache way was just to do 2^{1-k} < 2^3
which implies {1-k} < 3 -> -2 < k
you are, once again, going down a painful route.
you could write your ineq as $2^{k-1} > 2^{-3}$ right off the bat and solve it in seconds!
Ann
btw could you confirm the "general approach" i used
like is the process as said?
The answer comes to be right ofc
just want to clarify
your 'general approach' is probably okayish but poorly suited to this scenario...
okay sure
thanks for the alternative way
and clarifying my query
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@kindred storm
Rank is possible only for square matrix
So maximum rank is 4
That's why I cut the option first
wdym
are you sure that notation stands for rank?
it think itb about the size of the matrix
@jolly sable Has your question been resolved?
100%
P sign is rank
Rank of AB will be equal or less than rank of A rank of B whatever minimum is
no, i meant the first possible option
i meant, thank you for telling me what p stands for
Which notation
but why did you cut the first option
can you send me again the exc pls
oh okay
sorry, i misunderstood the question before
yup, the first one doesn't apply here, they aren't square matrices, give me a moment pls
Moment is over?
Helpers are just people volunteering their time to help you. Be polite.
lmao 😂 i forgot how to do this, maybe i need more time
lets see if someone else can help
<@&286206848099549185>
yes
Like iv is also correct but the last one is that most apt
update, a bit confused between iv and last option
Answer is given 2
after thinking for a while, maybe i think i have the reasoning
@jolly sable Has your question been resolved?
Elaborate
GKAOGKAWKOTKAO rwaofpgk3p0l6-3o6-3op6lghlh- Im either BLInd cuz i dont find a way to join these things and have no idea about the statmentes provided above.cAN You wait 30 minut pls
or <@&286206848099549185> can someone help pls :3
*sighs*
alright so we have that BA = I4
I4 means identity which is invertible so it's full rank ie rank(BA) = 4
which means min(rank(A), rank(B)) = 4
also notice that their maximum rank can be 4
since both maximum and minimum is 4. Both their ranks must be 4
which implies rank(AB) = 4 as well
I think I know how to do it if rank(BA)=rank(rref(B)rref(A)) which I'm unsure for a reason
in an easier way
I'm gonna assume rank(BA) = rank( rref(B)rref(A) ) = 4
@jolly sable Has your question been resolved?
I think I have it, but... I also reached a conclusion im not sure if its true
this conclusion: ~ If A size 7x4 and B size 4 x 7 and BA=I, then rank(A)=rank(B) ~
Let B be a 4x7 matrix and A be a 7x4 matrix, It's given that BA = I_4. First, we know that rank(BA) = rank( rref(B)rref(A) ) = 4. From BA=I_4 we know that there are either or 4 independent columns in B or 4 independent rows in A, Because rank(M)=rank(M^T) for any matrix M, if that's the first case then there would also be 4 independent rows in B, or otherwise 4 independent columns in A. Let's analyze the first case. Because there are 4 independent columns in B, rank(B)=rank( rref(B) )=4. At this point B could have 4 of their colums be independently out of the possible 7. Because swapping columns does not affect the rank of the matrix, we will now set B' to be an adjoint matrix [ I | 0], and we could think of swapping rows does not affect the rank of the matrix too, but its not necessary since entries above, below, right or left of a pivot are always 0, so doing this step already organizes our rows. Reorganizing A in the same way would lead us to A' = [ I/0 ]. Therefore, because A' has an I matrix adjointed, it would imply A has also 4 independent columns, either case rows. Now we can do the same argument for the case rank(A)=4 and rank(B) is unknown. Because both arguments lead to same conclusion in both directions, we can conclude strictly that A and B have 4 independent columns. Now we can only use the fact that A has 4 independent columns to conclude that the columns of AB are just linear combinations of the columns of A with the coefficients along columns of B. Therefore, rank(AB) = 4
this argument shows the case 4-independent 4-independent or viceversa, so Rank(A)=Rank(B) additionally as additional conclusion?
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Hey I jus loss the channel for help
I was talking to someone on
It was how to
Shade the area of the triangle formed between the y axis and two straight lines. Calculate the area of this triangle
Hey guys
Can anyone help me
Sketch a graph
I don't get
How to shade the area of a triangle formed between the y axis and two straight lines
And find the area for it

Yes
So I dk which triangle to use
On the question
Which triangle between the y axis and two straight lines?
R those the 2 lines?
@icy anchor Has your question been resolved?
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Do u know Chinese remainder theorem
Have you tried applying Euler's theorem?
Hint: || consider doing it mod 7 and mod 19 first||
yes
Is that saying too much idk
2^132=1mod133
That is not what Euler's theorem says
2 should be remainder
see
.
That is not Euler's theorem
i am saying fermat theorem
It is $a^{\varphi(n)} = 1 \mod n$
i solved it with fermat
A Lonely Bean
Fermat's little theorem is useless in this case until you consider different modulos
Because 133 is not prime
So it's better to go with this
Where phi is the Euler's totient function
,w 133 * (1 - 1/7) * (1 - 1/19)
Yeah
There is your answer 
I have a idea
what if we seperate like prime numbers
May work as well yeah
but how will we do 2^25 in the exam?
I got 128 by seperate them
and use of fermat
Just subtract 128 from 133
then
read the full convo
you can directly apply fermats
yes i did
i am asiking how will we get answer by lonely bean method of euler
i meant we are stucked at 2^25
you would get
2^25= 1 (mod 133)
lmao
,w 2^25= 1 (mod 133)
108
2^108=1 mod133
we can if we seperate
ok got it
7*19
now what you do
but i want to solve it by euler fully
what
okay
you are doing a long method
we are here 2^25=mod133
this isnt long
yes and in 2 steps
you have answer
im literally now using properties of modulo
2^7* 218=mod(719)
after that point
i am trying to use of euler
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,w 4x^2 -(3x+2)^2 factorise with explanation why it's equal to -(x+2) (5x+2)
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4x^2 -(3x+2)^2 factorise with explanation why it's equal to -(x+2) (5x+2)
_basudev
but how did we find 5 in (3x+2)^2
in this form
oooohh
4x² - (3x+2)²
4x² - 9x² - 12x - 4
-5x² - 12x - 4
-1(5x² + 12x + 4)
I just dont like negative numbers so took -1 common
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I found on a textbook: for every x != 0 and y two real number proof that x^2+y^2 > 0.
it seems so obvious that i don't know what to proof
not necessarily
yeah sorry I formulated it wrong
so there's your proof
but why putting that on a textbook -_-
anyway ty
I was just not sure if I missed something xD
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hi guys i was wondering how can P(A U B) = 1 help us in this question
What's P(A|B)?
P(A|B) = P(A and B) P(B)
It's P(A|B) = P(A and B)/ P(B)
Not multiplication
oh yeh mb i forgor the divide
Okay.
Enemagneto
yes but how can i get using this formula P(A), P(B) and P(A and B)?
i need P(B) for P(A|B) to get P(A and B)
Well, make use of the information given in the question.
Firstly, try to find a relationship between p(A|B) and p(B|A).
Nice
Now, put values of p(A|B) and p(B|A) in that equation.
You will find a relationship between P(A) and P(B).
@tame lance Has your question been resolved?
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Is option b correct?
I listed all the bijections from {1,2,3} -> {1,2,3}, and saw the function where 1->3, 2->1, 3-> 2 has the property 2
sure, I'm trying to answer the above question
I think symmetry group of three letters is same as set of all bijections from {1,2,3} to {1,2,3}
so I listed all the 3! elements in the set, ie 6 different functions,
where the operation is composition
yup
was my approach correct?
ie to to check composition manually?
or is there something simple?
suppose if I ask is x^12 = e?
is it easy to answer?
did you mean "which elements x ∈ S_3 satisfy x^12 = e"?
yes
ya he meant that
ya
i asked op not you tho
how does that help us here?
i'm pretty much a starter
i think i saw you ask about the proof of lagrange's theorem
it's either the theorem itself, or a corollary thereof, that for any finite group G and any element x ∈ G, x^|G| = e
so if |G| divides k, a^k =e also?
of course
makes sense
exponent laws still work just fine in a group
as long as all your exponents are integers obv
makes sense
i don't think it's me
started group theory less than a week ago
thanks again.
suppose I collect those elements a, such that a^2 =e
and put in a new set
will it form a group under same operation ?
@tropic oxide
well, that should answer your own question.
...
how does that change?
yes
aabb=e
or abab= (aa)(bb)= e*e= e
i guess so
yes
let me verify the group axioms here
since e*e= e, e is in H, so identity is there
associativity hopefully yes,
inverse is g*g, given
so group
is that okay?
@prisma gull Has your question been resolved?
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how to find total distance traveled using position vs time graph
find all points where direction changed and sum all individual paths
do i have to use distance formula to find the arc length
post the original question
assuming the graph is composed of just straight lines
You are not trying to find arc length, distance traveled is just change in position
Post the graph, it will be better to show it on a particular example
ok i just found this off google
let’s say this graph represented the position of an object
okay, so first try finding what distance did it travel going from A to B
dont overthink
is it just 15
do i not have to find the length of the lines
No
Why
Why yes? When it was at point A, it had position 0. When it came to B, it's position changed to 15. So the distance travelled was 15
no arclength
just change in position
so would the total displacement be like that as well
you would do final position-initial position
displacement is final position - initial position
total distance traveled may differ from displacement
e.g. when you go 10 steps forward, 4 steps back and another 5 steps forward your total displacement is 10 - 4 + 5 while total distance travelled is 10 + 4 + 5
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32x-12x divided by 143x
20/143x
!help
Please read #❓how-to-get-help
!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'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
1
20x
like terms combine
It is minus.
note that you could verify this by factoring out x to get x(32 - 12) = x*20 = 20x
Well Can you cancel the x?
Yes!
Well thank you for helping me.
Np
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What's the goal?
,tex .exp rules
riemann
use uh product rule
@eager wyvern Has your question been resolved?
how does that help me tho
answers this question
how
did you read the product rule
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factorize 16x^2 - 36/16
!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'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
I don't know where to begin
Do you know the formula for a²-b² ?
a = 16x^2 and b: 36/16 ?
Be careful as we're looking for a²-b², not a-b
We're getting a bit closer but still not there
So yes we want a² = 16x² in a first part
So what is a ?
oohh so a= 8x
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✅
factorize 16x^2 - 36/16 I have begun but got stuck midway
i know now that a= 4x
so a²= 8² is that right?
anyonee?
Sorry
np
a = 4x is correct
yay
Correct !
yyaay
so a² = 4²x² and b² = 36/16
is (a-b) (a+b)
but its 1.5
Yes
We can find a smaller denominator to express 6/4
Do you know how it can be written?
Np
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.solved
Hello! I need help. On function and non-function
Just giving me examples
And I identify
It and if you could use a verbal descriptions
For example
If a person is watching a football broadcast streamed to a million people, is that function or not a function?
I don't have a specific problem because my teacher has a specifically given me any practice. So I'm asking you before my test. This is going to be easy. It's just I want to have more practice from some people that are
Better in the topic than me
Well, what is a function
Alexis
The relationship
Or a relation?
Between the x and y
Each set having one input and output
You could use the VLS or the vertical line test to see
If it's a function or not a function
The rule is if it passes more than once
Then it's not a function if it only goes through once it is a function
A function is simply a mapping between 2 sets, the input and output set, where each element of of the input set is mapped to at most 1 element in the output set
Yes, I already know
What I'm saying is just to give me examples
Like the one I gave you earlier
Or even just a whole worksheet
Or something like that
That’s not what you said when I asked what a function is
Since I never got any practice problems
It's along the lines what you said
I'm just going based off with my teacher saying
What you said was not precise and not always true
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The question is in this image. Due to the phrasing of the question, it appears that there would only be one answer, but I am unable to limit it to only one. Is there any other method?
What I did:
r = b2 - 1 / b + 1, r = 1 / b2 - 1
therefore (b2 - 1 / b + 1) = (1 / b2 - 1)
This can have 3 solutions. What am I doing wrong?
(I know that this is a silly question but I am confused :( )
maybe the idea that there are 3 solutions is an illusion. Do you know what b^2 - 1 can be factored to?
I think I see what you mean
Forgive my algebra skills but would it be (b+1)(b-1)
and as the first term is (b+1) r would be (b-1)?
your algebra skills need not be forgiven for this is correct :)
thank you!
r = b-1 yes
I will take another crack at it with this information
I have a result of 1.205
I believe this to be correct, thank you for the help
👍
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i cant seem to ever understand why if we root both sides in the final step the plus minus goes to the root 10
why is it plus minus root 10 instead of just root 10?
if possible could someone explain conceptually as possible ;-;
the same way that when you have for example 4
both 2^2 = 4
and (-2)^2 = 4
if you want the rigorous justification :
i know but why dosent the x turn into plus or minus
oh the last line is the same as $\pm x = \sqrt{10}$
rafilou2003
but here's the rigorous way to show that :
Because for $\sqrt{x}$, the domain is $x \geq 0$ but with $x^2$ the domain is all real numbers hence $\pm$, idk if that answers your question
what does the upsie down question mark mean?
It was supposed to be x >= 0
ohh
But latex messed up the formatting
gotchu
x >= 0 yes
The function $f(x) = \sqrt{x^2}$ is equivalent to saying $f(x) = |x|$. As a result you should consider both plus or minus.
yeah, $x^2 = 10 \Longleftrightarrow |x| = \sqrt{10}$
rafilou2003
(over the real numbers)
but I feel like I did many questions like that where I took the square root of both sides and didnt end up having the plus minus sign
maybe because you knew x was positive
is that because my teacher didnt ask for that or beccasue there are some problems where it is not needed?
o like if there was a limit next to the equation going x>0?
uh not limits
you can ignore a negative from context of a problem: for example if it's asking you how many apples Abe has, it cannot be negative.
How I remember is, if you manually have to apply the sqrt, ie you wrote it, it's plus/minus, but if it's already there before you do the problem, then it's just plus
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$\lim x-->x \frac{1}{x}- \frac{-1}{senx}
Kangaroo
$\lim{0} \frac{1}{x}- \frac{-1}{senx}$
$\lim_{x\to 0} \frac{1}{x}- \frac{-1}{senx}$
Kangaroo
I need help with this problem, I need to apply to L'Hôpital's rule
so you know l'hôpital applies to a quotient
also did you put one too many "minuses"?
$\frac{-x+senx}{(senx)x}$
Kangaroo
this is good ok
maybe is better on the initial from
but i would use the fact that sen(x)/x has limit 1
no this form is better
okay
Mhh, why?
write this as
$\frac{-x + sin(x)}{x^2}\cdot \frac{x}{sin(x)}$
rafilou2003
the thing on the right has limit 1, so we can discard it if we're looking at the limit in 0
as for the term on the left, what does l'hôpital give us?
Sorry why limit 1?
whats sen btw
sen is sin in spanish
oh, okay
Yeah it is confuse
yeah
The right thing would be sin(1) no?
? no
So why limit 1?
$\lim_{x\to 0}\frac{sin(x)-0}{x-0} = ?$
rafilou2003
Oh okay
Because x->0
so 1/(all of this) is still 1
i didn't understand this but ok
Haha
it is on my book in that way
But my book is more like a student guide than a math book
but the answer is 0 so it is correct
Oh no
I reach an indetermination not a solution : V
. close
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first 2 are definitely true, but how do you check the third one
@runic prawn Has your question been resolved?
see if you can find a counterexample
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What is the probability that the car is repaired under budget given that it is ready on time?
I don't know why I'm struggling with this
I keep getting stuck with odds that are way lower than they should be
last time I got like 13%
waaait
I feel like it's coming to me
nope
0.6554 this time
I know I'm closer to getting it but I'm still doing something wrong
YESSSSSS
.close
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what is the period of cotangent
and what's the difference between -17pi/3 and 4pi/3
21?
idk
21pi/3?
well you should probably find out
so what do I do with this
21pi/3 simplifies to what
Closed by @sharp kestrel
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what
what
7?
.open
.reopen
✅
21/3?
simplifies to what
pi/7
no
Austin
7pi
ok now what
sorry idk what that is
Trig functions are periodic
meaning that they repeat themselves over and over again
how often they repeat themselves, that is the period
,w plot y=sin(x)
ok
look at the graph
verify this for yourself
the period of sin(x) is 2pi
so if you had
ok
ok
so find cotangents period
and use the difference in between the two points you are evaluating
to make a judgement
,w plot y=cot(x)
pi?
yup
ok
ok
you can do the same thing forever
cot(-pi/2) and cot(pi/2) and cot(3pi/2) and cot(5pi/2) are all equal
why?
they are all the same distance away
yea
yes
so if you are pi apart
or 2pi apart
or 7pi apart (this should remind you of your original question)
they will be the same
so how do I get to 4pi/3
as you said earlier, the distance between -17pi/3 and 4pi/3 is 7pi
so this tells you that the cotangent of both are equal
ok how would I get to 4pi/3 if I wasnt given it
What do you mean by get to it?
like how would I know they are equal
because they differ by pi in distance
anything that differs by an integer multiple of pi
will be equal
in cotangent
but do i have to memorize that
unless you have more questions yes
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you're welcome
Thank you
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I have no idea how to even start this problem 😭
@abstract wing Has your question been resolved?
f and g are linear functions so you can write them like this : f(x) = ax+b, g(x) = cx+d, with a and c the slopes
a=2 so f(x) = 2x+b on (-1,+oo)
g(0) = -2, so g(x) = cx-2 on (-1,+oo)
f(x) > g(x), therefore 2x+b > cx-2
🤔
you can already determine some information about the slope of g given the first two sentences
if the slope of g were less than 2, then eventually f and g would cross somewhere in (-infinity, 1)
@abstract wing Has your question been resolved?
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I don't know how to solve this😭 The blue is the given and is being found. The red is my attempt at least
I'm not sure how to get the domain
what's the solution to this? learning~
no like how it went to x^2 + 4x
wdym? 
the bot earlier answered the question i think
yea that was me, you're having trouble expanding? :)
yeah, I'm a bit unfamilliar with this
(x+2)² = (x+2) * (x+2) = x² + 2x + 2x + 2² = x² + 4x + 2²
They didn't teach it at my school before
$(x+2)^2=(x+2)(x+2)=x(x+2)+2(x+2)$
MrFancy
there are often many methods to expanding/factoring, find which way works best for you :)
onto the actual question, how could you get the domain of x²+4x+9?
how..
is there any number that you could plug into x^2+4x+9, that would make it undefined? 
0?
why would 0 make it undefined? 
it's not a real number-
0 is very real mein freund
testing my stock knowledge IEJSFOIJFES
can you tell me what $0^2+4\cdot0+9$ is equal to?
MrFancy
9
notice all I did was put zero into the x's in the quadratic before ^
and is that undefined? :)
nope
ok so that means 0 is in the domain
is there any number you think that would make the function undefined?
why would -9 make the function undefined? 
(-9)^2+4*(-9)+9=81-36+9=54 and 54 is very much defined :)
joke wait
Hint: there is no number that makes x^2+4x+9 undefined
ack
that means the domain of this function is every real number
do you know how to express that in interval notation? :)
ah infinite
Consider it this way, the domain are all values for x for which the function is defined, therefore instead search for all cases for which the function is not defined. This includes division by 0, taking the root of a negative number, 0⁰ etc
this one
not quite
just putting infinity doesn't tell us a whole lot, do you know interval notation?
ok that's fine, if I had the interval: [-3,5] do you know what that means? 
it means the range between -3 and 5
so -2 is in that range
1 is in that range
but 69 isn't
nor is 420
ohhh
that make sense? :)
yes yes
so would 1/2 be in the interval [-1,1]?
yes
yep! ok so do you feel comfortable with interval notation so far?
ok very good, so I have one more thing to add, there is a differnce between [] and ()
and the difference is important
[] means the end points are included
so if the interval is [-3,5] then -3 and 5 are included in the range
but if we used parentheses
oooooh
yupp
ok, so what would the interval notation be for all real numbers? 
yes very good! but one final question do we use square brackets or parentheses? 
why?
hey you're learning pretty quick
5 mins ago you didn't even know interval notation
they are included within the range, and it's infinite?
but infinity is not a number, so it relaly cant be included itself
ohh
so whenver there's an infinity in interval notation
we use parentheses, make sense? :)
yupp
ok, so finally, what would be the domain of this function?
yep (-inf,inf)
wdym by interchanged? 
like (inf,-inf) and vice versa or is there just supposed to be 1?
we always go from left to right on the number line, good question :) negative to positive
icic
there we go, hope I helped you not only answer the question but understand math a little more in an intuitive manner 
neat introduction 👍
thanks for being patient
if you have any other question I'd be happy to help otherwise you can type .close to close your channel and I hope you have a very good evening mein fruend
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Hey all
I'm a bit confused about something
Green's theorem is supposed to let me treat this as a double integral over a region
Simple enough
But every example solution I'm looking at is saying something about "having to break it into two curves, and find the line integral of each"
Is the whole point of Green's Theorem not to treat the problem as a double integral?
...
Am I supposed to be working backwards? Starting with the double integral, converting to a curve, and then solving for the line integral?
yes, that's exactly what you're supposed to do here.
Ahhhhhhhhh
the double-integral interpretation comes directly from the fact that you're computing area
And because, once its framed in the context of a line integral, it isn't smooth
namely that the area of a region is the integral of the constant 1 function over it
@old monolith Has your question been resolved?
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could someone walk me through ∫ arctanx dx
or help me get started with it. it's not homework, I'm just sitting I'm bed and I'm realizing I have no idea how to do it
do parts
mm how would you split it in parts?
1 * arctan(x)
Yep
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Hello,
I have $f(x) = 4x^{3} - cx^{2} + 2cx -4c$.
I am trying to show that for any real and positive value of c, f(x) doesn't have three positive, distinct, and real zeros.
I have narrowed it down to showing that $f(m)\cdot f(n) > 0$, where m and n are real zeroes of the f'(x). I have already ascertained that m and n are both positive for f'(x) under restrictions on c. For real zeroes of f'(x), we have constricted c values to be greater than 24.
Now, doing this last part seems highly computational(since m and n are in terms of c, and are in form of roots that we get from quadratic formula) so i have, obviously, not proceeded. I was hoping if someone could enlighten me with a way of making it simpler.
Any other way of approaching the problem is welcome as well. Overall, i appreciate any useful input whatsoever.
Thank you.
Enemagneto
@lunar lynx Has your question been resolved?
i am bad at these kind of problems but
could you make some kind of argument with the inflection point of the cubic
since its so much easier to find exactly where it is
i know thats not really helpful 
maybe something like this? https://math.stackexchange.com/questions/3440575/what-is-the-main-relationship-between-the-inflection-points-and-the-roots
just spitballing, hope you have luck
original polynomial?
Yes
I brought a geometry problem into algebraic form so "sus" is inevitable. 😶
Let me try.
Yeah. I can show that but i still wanted to learn this way as well. It's a proper translation of the problem with no missing info(i think).
@muted bear
Interesting
Honestly, i'm bad at geometry so i couldn't think of anything else but to do what i did.
Woah. Multiplying with (x+2) seems good. Terms of x^2 and x vanished.
But i don't really see what to do with that.
What polynomial do you get?
$4x^{4} + (8-c)x^{3} -8c$
Enemagneto
This was nice to learn but i can't see how that helps me here. Thanks, jan Niku, nevertheless.



