#help-26
1 messages · Page 225 of 1
Ok its back I just had to restart the laptop again
So if domain was all reall numbers then... I believe the range is?...
And that was just the function it's self....
Now I need to search for y=|f(x)|
Domain
does the absolute value have a restriction on its inputs?
The outcome can never be negative
sure, but i asked about the income
Can you define what an income is?
the input
if i have y=|x|, whats the domain of that
|x|= x
lost me a bit there
I think I am just as lost
So this is what I have
I originally thought I needed to take the given domains and lay them out
i can tell you that the absolute value has no effect on the input functions domain
because it takes all of R
So (-si,si)?
but from the graph we can also see that
aye
The range though...
it is indeed, we know that because f crosses the axis
So the range would be [0,si)?
AℤØ
I cant tell if you were in the Navy or you enjoy talking like a sailor
just spent a fair amount of time in scotland 
Oh I understand- you are from the UK nice
Ok so I figured out the absolute value of the last one but the domain for this absolute value is... tricky
I could use the given pointz
what are your thoughts
Well, the function is f(x)=sqr root x
But the line starts from -3
But the absolute value cant be negative
it still isnt negative
So... would it fold over the y axis?
are there any negative y values on that graph?
Making it domain for y=f|x| is [3,si)?
nope
youre confusing the input and output
the absolute value can take negative inputs
So then would it be [-3,si)?
it would indeed
the absolute value only affects the output
How do I not mix up the two? Know any simple or specific methods?
That might be asking too much belay that...
think of it as the distance from 0 of x
well in this case f(x)
what goes inside of the absolute value is the input right?
Yes
what comes out is the distance from zero of that input
-3 is 3 away from 0 on the number line and so is 3 so |-3| and |3| are both 3
Yes
thats it idk if that helps
It does
great
The input is usually (x +/- a) the output is -/+ b
From what I understand in your phrasing
So in this case the range sqr root function of |f(x)|= [0,si) ?
I see
because \sqrt{x} never has negative outputs
Aw...
are you talking about this graph
Yes I was
oh ok then it is a bit different
so the absolute value is the same for both functions but the domain is different
that function is \sqrt{x+3)
a sqrt can not have a negative inside therefore the domain should not include any x that make x+3<0
what do you think the domain is then?
It would be [3,si)
close but no
Oh
Ok I understand that one now
good
well first what do we know about absolute value?
It cant end negative
correct whatever goes inside must leave as its positive version
And the range is an output?
in this case f(x) is our input for our absolute value
f(x) has a negative value within its range correct?
Correct
so since f(x) is having the absolute value taken of it, the minimum value of |f(x)| range must be the absolute value of the minimum value of f(x).
which is?
Can we back track a little?...
ok
Is this something to visualize on a graph?
How would that look?
see f(x) has a range of [-1,inf) , f(x) is the input for the absolute value so the range of |f(x)| has to be the absolute value of the range of f(x)
you need a function to use with it we dont have one provided so idk
Soooo [1,si)?
Wait- the system says its wrong???
?
hmm it seems to be because since the absolute value make -1 to 1 but also supports 0
that is why
no yes they are right
Alright
[0,si)
So say if there was a range of [-5,si) its absolute value would turn to [0,si)?
yes
because the negative values would be mapped as positive and then 0 would be the lowest value for |f(x)|
Ah...
that was my bad, sorry
indeed
ok so first find the minimum value for (x+1)^2-3
just graph it
it would be easier to do analytically
Oh- right-
I cant rely on a graphing calculator (not allowed for test) so I want to make sure I understand this
ok good have you found the minimum value
well that equation is in vertex form
if u know the vertex then u can find the domain and range
correct
the range should be the y coordinate of the vertex to infinity and domain is -infty to infty
So for my sake- this is is the correct visual right?
this is for (x+1)^2-3
for which one?
The absolute range... eh...
what do you think so far
So [3,si)
no
Oh.
range is the minimum value of the function to the maximum
Its unending
so since absolute value only allows the y value to be a minimum of 0
then the minimum is?
yes so the range is [0,si)
your graph is correct
The domain is.... [-6,7]?
yes
for f(x) yes
but for your coordinate at the bottom (-6,1) its wrong it should be (1,-6)
apart from that so far so good
Yes I did fix it after I noticed
good
Lets seee the domain stays the same
yes
The absolute range is...
....
[0,7]?
good job
On to the next one⚔
much better
Do you know good plaves to practice (that do not cost money)?
Khan acadamy is good
yeah you can do that
Even though the email is long gone
well you can always make an account
if you don't have any further questions or think you are ok close this channel
I still do
alright bet
Annnnnddd back to zero understanding.
gulp
thanks
No prob
oh ok very simple
we have the two functions y_1 and y_2
and we want them to be equal what numbers would do that
aka where both functions intersect
what x value(s) makes them equal
Ehhh...
Dont tell me... do we have to find slope?...
no no
Phew
-1 and 2?....
Wait really???
Yesnt
? what
The points are a ray they arent intersecting
the blue and red functions intersect and x=-1 and x=2 making them equal
Ohhhhhhhhh
see how in the coordinates shown they have the same y
those are just the names of the functions y_1 and y_2
you picked the wrong one
there were various
yup
well sets in general
but yeah
(-1,2) would imply the point (-1,2) or a range/domain which neither are solutions
So what would be solution be?
{-1,2}
Here
thanks
No problem
ok so find the domain where the blue function is less then the red one
How would I write this?
interval notation
Soooo (-1,2)?
yes
So the other stuff is just there to throw it off?
Yes
they are there because they are an answer to a question but it can throw you off
I wanna say... D?...
I dont fully understand that one but it just occured to me Im at question 12... out of 27...
Of 2.4... I havent gotten to 2.6 or the review (approximately 30 questions each)... and I have to take the test tomorrow...
@ruby wedge i can take over if ur ok with it
Oh shoot- sorry dude
dont worry about it
ur good dw
What are the odds I finish this all before the test tommorow?
100%
I mean I can take it at any time- I just have a time limit...
ok so we're looking for the graphs intersect right
Yes
and how many points are there where they intersect
One
so what choices can we eliminate
so whats the answer
Wait- do I need to plug in the equation?
Im looking for the solution to y1=y2 apparently
well yes ik that
but have the previous problems asked for a coordinate
or just a y value
i just searched it up
B is the answer yes
just the x value
Ehhh now I need solution set for y1 < y2?
send me the problems pls
Its a line ?
The red?
Im so confused...
The one with absolute value is the only curve I thought
The blue one
Yes
where
Where is the y1?
y1 is the blue function
Im going to assume Im over thinking this again💀👍
you are trying to find what values of x make the blue function greater than the red
im back
is the red curve above the blue curve
To see if its its then y2???
At least I think my notes say something?
No the blue is above
well i mean u can sorta look and see that the red is never above the blue
and then use process of elimination
no?
yeah
So 1 and -1?
So its 1 again???
so at every other point it is greater
what answer encompasses every x value except 1
what does greater mean
@neon iron lowkey this is becoming a two person job
It means y1 is less then y2
yes
so on a graph how would that look
I wanna just say theres no solution
there is
But its probably A?...
umm yk what A means?
yeah lets not guess
I dont understand how its 1 and 1 when then line isnt even on the orgin
what does that have to do with the origin
thats not the origin
HOW IS THAT 1
ummm look at the x axis
...
it goes by 2
so half is 1
lets go back to the basics you have a function right? the function has an input and output essentially the input (x) value dictates the output (y) the height of the function so if the height of the blue function is higher than red one there are x values that make that true you want to find those
x values that make the blue function greater than the red which is all of them except for 1 because they are equal to eachother at that point
Thank you for trying💀⚰😭
i have taught before so
@neon iron I appreciate it
alright you and me again
Ok ok maybe A visual would help?
alright let me make one real quick
Or maybe I should get back to this question later
Ok
nah i just need you to understand why it is a
I want to as well but the puzzle is not piecing
did you read my explanation
its not a 😭
But its not... I need a visual
but its the one that excludes 1
ok ok
im tuned to domain for intervals 😭
lol its okay
how would u do that
Probably not
how is that even possible 😭
Hold on its in my notes
💀
icant make a visual
plus im more of an analytical person
anyway you dont need to do anything to the function
I am also analytical... in the most useless way right now
its literally graphed 😭 why would u want to work with the actual equations
we found out that when x=1 , y_1 is equal to y_2
yes
I dont know maybe it would give me a sense of control or something 💀
yea but hows that hlep
so at every other x the blue function is larger than the red
I cant figure out where the negative one is from
so there are two intervals where the blue is larger (-infty,1) and (1,infty)
Ohhh...
if you combine them (union) then you get the answer a
So the answer is A....
I was focused on the numbers and point its self
Computer saying incorrect
oh so we are looking for the opposite mb
The opposite makes more sense then this one
I just wanna put no solution so bad
if the blue one is y_1 then it is no solution
Because tell me where a -1 just appears from
Rainbow what grade r u in
prolly highschool
College algebra
Yes
Well I’d think so
okay probably a freshman
I havent done math since I graduated school 4 years ago 💀
damn
@neon iron what was the highest math you studied or studying
I failed the first test because it started with a camera looking at me a timer and a white screen - suddenly all that I spent weeks learning just- poof...
I’m uhh doing abstract algebra rn… I’m at a private hs and they let me do classes at a local community college
I’m actually doubling
me too
Long story went to military had medical discharge yada yada
As in ur doing abs algebra as well
I used to be good at this...
Or as in ur hs let’s u take classes at a local college
I did dual enrollment
topology
But in my final year (because transportation issues)
as in dual enrollment
Also covid did a number
applied to MIT a few days ago
Oh my gosh there it no solution this entire time...
Congrats
Mit or caltech
Hope you get in
yeah wish me luck
Good luck man
MIT
oh yeah fs
I should have just put no solution from the start💀
yeah
This entire time I spent...
your family is intellectual asf
Umm great parents
im the outstadning one in my family
Yea
gotta represent
lol i have fun with it, its competition
Hey but pressure makes diamonds
I have a diagnosed learning disability:D
Pressure is a privilege
oh
Maybe 2.. other ones
holy bomb drop
But thats not offical yet
@ruby wedge can I friend u
fs
You guys have no learning struggles? If so, I'm glad for you
I might have autism- I mean everyone seems to ask me if I do (and its never jokingly) buttt its a shame the possible benefits are cancled out by the Adhd._.
I get the hyperfixations - but only if they give a LOT of dopamine
Anyway back to math
Im now dealing with... this.
Oh wait I might-...
Nope.
@ruby wedge @neon iron sorry for getting off topic
your are good
I believe so but let me just test this one and if I do I will skip and work on this specific part tomorrow
Alr alr
I think I do something like...this
Alr alr
Good job
x can technically be both
After checking
So would that make the solution set (6,-12)?
Yea
Im going to guess its not points so its the finite number set with these{} instead of ()
Yea
lowkey i havent done this in a while so idek
Show me the answer choices
Im wondering if I should try to finish this tonight or if I should pick it up tomorrow with a fresh mind- even though well- the test is tomorrow.
I wish at the very least we could keep basic formula notes next to us
Ah- the first one.
I see
Hm...
i would say pick it up tmrw
Yeah I feel like the later it is the more things are... slipping like... sand perhaps
I'm just nervous
I didn't anticipate that my plan to work on the second chap through the week would get interupted by 4 days sick
It’s alr u got this
yout welcome
Maybe its is best to pick it up early tomorrow
yup
Thank you so much for the help
I imagine I took up alot of your time
@neon iron @ruby wedge Hope you have a good day/evening
I should probably close this up for now right?
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Hello. I wanted to solve Hatcher's Algebraic Topology exercise 1.1.1.
Send an image of the question please
It says, show that composition of paths satisfies the following cancelation property: If $f_0 * g_0 \simeq f_1 * g_1$ and $g_0 \simeq g_1$ then $f_0 \simeq f_1$
Gol D Roger
I need to construct the homotopy, but Idk where to begin
To be more precise, the question is this:
<@&286206848099549185>
Well you can compose with the inverse path of g0 on the right of both sides
Like $ f_0 \circ g_0 \circ g_0^{-1} \simeq f_1 \circ g_1 \circ g_0^{-1}$?
Ye
Ok, I suppose the left side is homotopic to $f_0$. What happens to the right side?
Gol D Roger
Since $g_1$ and $g_0$ are fundamentally distinct
Gol D Roger
Well theyre given to be homotopic here
Since theyre homotopic endpoints are fixed right
Yeah
Idk if this was mentioned in the text also but if g_0 homotopic to g_1, then g_0, then g_0 o f is homotopic to g_1 o f
So therefore g_1 o (g_0)^-1 (using this inverse notation) is homotopic to identity
I dont have the latex off the top of my head sorry
Don't worry, I think I understood what you mean
But, do I have to specify why the first part of this works?
Since I think is using what I need to prove
Like, the composition property
Of homotopic paths
This one isnt too bad, you just find a homotopy X x I -> Z given f: X->Y and a homotopy H: Y x I -> Z (between g_0, g_1)
Namely you take H and you precompose it with a function f x Id_I: X x I -> Y x I, (x, c) |-> (f(x), c)
So H o (f x Id_I) is a homotopy X x I -> Z (you can verify this)
Ok, I'll write it then. If I conclude it I will close. Thanks for the idea
Theres a similar one but with postcomposition which you might need to finish the proof too
Which one is that?
Like f o g_0 is homotopic to f o g_1
If g_0 is homotopic to g_1
The proof is entirely analogous you just postcompose with f
So, what you say is to prove composition left and right are the same?
No so like what im thinking here is
We have that id is homotopic to g_1 o (g_0)^-1
Thus using that, we would have that f_0 homotopic to f_1 o g_1 o (g_0)^-1 is homotopic to f_1 o id -> f0 homotopic to f1
You'll need to check this is true by verifying the endpoints are the same
Which should be true by defn of homotopy anyways
So from this you could construct an explicit homotopy sure
But you dont necessarily need to write out the homotopy to show things are homotopic (this method doesnt really require an explicit homotopy to be constructed)
Wow, that's really nice to read
Ok, I'm going to fill the details on what you've told me.
I will close as soon as I'm done
@sturdy fulcrum Has your question been resolved?
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<@&286206848099549185>
nah
Too early?
!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
2
Send us your best attempt
Absolute nonsence
it's a sequence of odd numbers starting from 175 and going backwards
Yes ik the answer but I need a way to write it
T(n) = 175 - 2(n - 1)
positive so T(n) > 0
175 - 2(n - 1) > 0
175 - 2n + 2 > 0
177 - 2n > 0
2n < 177
Thank you
n < 88.5
np
Don't give full answer, please? Give hints instead
Also the answer is 88, but I get 88.5 so yea
Don't know if that counts
Bc 89 is also an option but it's wrong
What is the value at index 89?
Yes. So you know that the number at index 1 to 88 is positive
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can someone explain to me how you are supposed to get the x = expression please?
@haughty drum
well you want some irrational number between a/b and c/b. So let's try to find an irrational number between a/b and (a+1)/b
so, we only need to find an irrational number between a and a+1, because then dividing by b makes it an irrational number between a/b and (a+1)/b
so, we only need to find an irrational number between 0 and 1, because then adding a...
so... pick your favorite irrational number between 0 and 1
any will work (so 1/sqrt(2) = sqrt(2)/2 works for example)
also for future reference, it's @ Helpers, not @ Helper (you pinged a specific person)
(and wait 15min before using that ping)
ah ok thank you for answering back I thought there was a special reason for picking sqrt2
also i didn't realize i pinged the wrong ping sorry
why is it a+1/b though? where is the a/b
try splitting the fractions into two parts
split it into numerator and denom?
(a+1)/b, not a + (1/b) jic
and (a+1)/b = a/b + 1/b
if we want an irrational $I$ such that $\frac{a}{b} < I < \frac cb$
why is it important to make the distinction of (a+1)/b
Raphaelisius Maximus MMIII
since we have $\frac{a}{b} < \frac{a+1}{b} \leq \frac cb$
Raphaelisius Maximus MMIII
if we manage to find an irrational $I$ such that $\frac{a}{b} < I < \frac{a+1}{b}$
Raphaelisius Maximus MMIII
well first between a/b and (a+1)/b
yeah
and then between a and a+1 as we multiply by b
yeah
(and then between 0 and 1 as we subtract a)
if it helps you we can do it
since a is rational (an integer)
if we have an irrational I between 0 and 1
then a + I is an irrational between a and a+1
and we win
yeh
when we said we only need an irrational between a/b and (a+1)/b
it's this portion that explains it
why do we need to metion c if all we need is a+1 and a
because we need to prove that we don't need c
whut
if we don't need c we need to prove that we dont need c by saying c exists?
im very confused
let's start from the beginning
we want to show there is an irrational between any two rationals
so... take a/b < c/d any rational numbers
"d" isn't needed, because we can take a common denominator
so take a/b and c/b with a < c
yes
since we have $\frac ab < \frac{a+1}{b} \leq \frac{c}{b}$, we can be even pickier and ask to find an irrational between $\frac ab$ and $\frac{a+1}{b}$
Raphaelisius Maximus MMIII
because in that case it'll be between $\frac ab$ and $\frac cb$
Raphaelisius Maximus MMIII
so we don't need "c/b" anymore
see how this lets us simplify the problem step by step
ok
we needed to justify every step
but now we don't need "d", and now we don't need "c" anymore
now let's push this further
saying we don't need "b", because if we find an irrational between a and a+1, then just divide by b
but we don't need "a" either, because if we find an irrational between 0 and 1, then just add a
-# Side discussion: Is the wording in the question is wrong? I think it should say “Between every two distinct rational numbers”
(it's implied, let's not be that picky about the wording)
@dark quest is there something you want to go over from those last two steps?
alright
trying to figure out how I'm supposed to come to the proof by myself
im studying for a exam and i am not very confident in proofs
and its very late at night lol
it's not easy but yeah simplifying helps
i get the problem now though tyvm
less variables = easier problem
ok i will try to remember that for tomorrow 
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I see that 10! is the total amount of outcomes and somewhat see that 4!3!2!1! represent the amount of repeats we have but since there are four different nationalities shouldn't there be 4! ways of getting these extra counts so shouldn't it be 10!/4!4!3!2!1! instead of 10!/4!3!2!1!
@graceful cove Has your question been resolved?
i think the assumption is that the outcome is like
1 Russia
2 United States
3 United States
4 United States
5 Russia
6 Great Britain
7 Brazil
8 Russia
9 Great Britain
10 Russia
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hi, why is this k value not a solution?
thanks in advance.
according to the conclusion in my book, only k = 1.975 is the right answer
Because that basically corresponds to k = 0, which would give you the function f(x) = 1. But the integral of this between 0 and 1 doesn't equal π
k being something like 10^-15 is very likely an index of a numerical error
ohh i see
understood
thanks
.close
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can someone give me introduction into proving things in maths with short example?
@autumn timber Has your question been resolved?
@autumn timber Has your question been resolved?
What is the problem?
@autumn timber Has your question been resolved?
i dont think I understand how you can prove something in maths and if you can add some simple example
A proof is a sequence of logical steps that start from axioms, and use what you already know to make logical implications
An example that you should be familiar with is solving equations
lets say you are given the equation x^2 - 2x + 1 = 0
by solving the equation in the real numbers (and providing all of the steps) you prove the statement "if x is a real number, then x^2-2x+1=0 if and only if x=1"
so i dont have to write the fancy stuff for everything?
wdym?
define "the fancy stuff"?
@autumn timber Has your question been resolved?
for example take a look at the proof of 1 + 1 or golbach's conjecture
it depends on your level of math
usually when you learn math, there will be assumptions you need to make, so as not to prove everything from the ground up every time you want to use a result
for example, you will never have to prove that 1+1 = 2 when taking calculus courses because it is accepted as true, and because the point of the course is not to prove it again
in short, you don't need any fancy stuff to write a proof, it just needs to be logically sound
well I need to learn something more for one competition, its like 4x harder than math at normal school and they require a lot of proving, example from last year is that you have some 4 letter number and prove that there is ab + cd = sqrt n; cd - ab = 5
or smth
more like how many exist and find something
also there were a lot of geometry proof, so yeah
as bloubb has stated, it really depends on what you're allowed or assumed known at that point.
You usually prove stuff not from ground up, but from what is assumed known.
In geometry, for example, you'd be allowed to use pythagora's theorem, without any need to prove it, because it's assumed known
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,rotate
ok so im at the last step but im a lil confused
why is x =4 or =0? its not exactly clicking
btw hello
forgot to be polite
$f'(x) = 3x(x-4)$, a critical point is when $f'(x) = 0$, so you find the values of x where $3x(x-4) = 0$
Stitches
Or do you not understand why 3x(x-4) = 0 when x = 0 or 4?
so this is saying that hwen the derivative of a function is = 0 meaning 0 slope meaning 0 change we must find the values of x this happens at?
the latter
i get the factor
the the derivative
and the derivative
Yes. The derivative of a function being 0 means that the slope is 0. This might correspond to a maximum (thing tip of a parabola), a minimum (think bottom of an upside down parabola, or an inflection/saddle point (ie. neither, think x^3 at x = 0)
what exactly is an inflection - a kind of center on the parabola?
its just why is x = 0 or 4?
It is where concavity changes
so you’re not confused about how to get f’(x) itself just why x=0,4 ?
yes
You have done quadratics before ? It is the same thing as that
thanks
not really
but i understand now thanks
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I am preparing for a linear algebra test, where I am allowed to use python. I have a problem with linear codes.
import numpy as np
def p1_of_list(bits):
return (bits[1]+bits[0]+bits[2])%2
def p2_of_list(bits):
return (bits[1]+bits[0]+bits[3])%2
def p3_of_list(bits):
return (bits[0]+bits[3]+bits[2])%2
def generate_paritycheck_matrix(n,k):
A = np.zeros((k,n-k))
index = 0
for bits in np.identity(k):
A[index][0] = p1_of_list(bits)
A[index][1] = p2_of_list(bits)
A[index][2] = p3_of_list(bits)
index = index + 1
return A
def generate_generator_matrix(n,k):
return np.hstack((np.eye(k), generate_paritycheck_matrix(n,k)))
#from here it does not make any sense
n,k = 7,4
data = np.array([[0,0,1,1]])
hamming = np.dot(data, generate_generator_matrix(n,k))
parity_check_matrix = np.hstack((generate_partycheck_matrix(n,k).T,np.eye(k-1)))
np.dot(parity_check_matrix, hamming.T)
The result of the last line is:
array([[2.],
[2.],
[4.]])
Which makes no sense to me, this should give index of the column that contains the error, no?
or in this case it should be 0, no?
Ayo
I am super afraid I don't get the theory
@winged basin Has your question been resolved?
@winged basin Has your question been resolved?
just show the actual question
This isn't an exercise, but I guess the question would be: Implement a linear Code System, which can generate the generator matrix, parity check matrix and check sent hamming codes.
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have a question about these two questions
why does one specify prime power order and the other doesnt
also can it be done without a calulcator
I was just going to find the orders of most of the elements to elminate which groups its not isomorphic to
for 27 G can be isomophic to either $Z_{16}$ or $Z_8 \oplus Z_2$ or $Z_4 \oplus Z_4$ or $Z_4 \oplus Z_2 \oplus Z_2$ or $Z_2 \oplus Z_2 \oplus Z_2 \oplus Z_2$
Branshi
this is from a chapter about the fundamental theorem of finite Abelian groups
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Hi, I'm Italian, I need help with maths, anyone speak Italian?
Mama mia
Are u italian?
inappropriate to say in this context, innit 😭
we got at least one Italian speaker among helpees and i can probably call him over but you should send your question(s) in Italian and then do your best to translate if needed
Uhm, ok, I'm not good speak english, but i can try. Where do i send a question?
here
I have a rational function x^3+x/3x. I can study the limits, but I can’t find the first and second derivatives, and I can’t plot it on the Cartesian plane.
what’s bothering you?
When I get to the first derivative, I can’t go any further. I could try to send a photo, but I’m not sure if you can read my writing.
please send
@pulsar forum Has your question been resolved?
There are limits shown at the top of the page, but please ignore them
The sign study is wrong, ignore that too. I corrected it on another page.
@pulsar forum Has your question been resolved?
@pulsar forum Has your question been resolved?
I'm sorry I can't really speak italian, but in that problem you can cancel the x in the denominator and numerator, when $x\neq 0$, so it should be easier to calculate the derivatives that way. If you choose to use the quotient rule anyways, you've made some mistakes while substituting the derivatives in the formula, it should end up being $\frac{(3x^2+1)(3x)-(x^3+x)(3)}{(3x)^2}=\frac{2x^3}{3x^2}$
KonoEmllikDa
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