#help-23
1 messages · Page 462 of 1
,w fundamental theorem of calculus
then F'(x) = f(x)
Ya
wait
im still confused
so it would just be F"(x)?
F'(x)
?
read the last line of this, and look at your question. Do you see what's missing from your equality?
FTC says $\int_a^b f(t)\ dt = F(b) \underline{-F(a)}$
Zybikron
f'(0), where is it?
so is F(b) and F(a)
you're not taking a derivative, you're integrating.
constants don't disappear when integrating.
yeah so wouldn't an integral undo a derivative?
up to a constant, yes
does $\int :f'\left(x\right)dx=f\left(x\right)$
Riemann Zeta Male
that +c is -f'(0) from your original question
sure
there, fixed it
so you're adding a negative constant
ur confusing me so hard
Using FTC, $\int_0^sf''(t)\ dt = f'(s) - f'(0)$
Zybikron
no it isn't
is it not true
if the whole integral was F(x)
and it were equal to F'(s) - F'(0)
?????
$F\left(x\right)=\int _0^s:f''\left(t\right)dt=F'\left(s\right)-F'\left(0\right)$
Riemann Zeta Male
what is F' tho
It looks like you're trying to combine both parts of the FTC and they don't work like that
I was trying to re-write $\left(\int _0^s:f:''\left(t\right)dt\right)\cdot :s$ and go from there
Riemann Zeta Male
but im not really sure if thats the right approach to continuing my solution
So you're just trying to evaluate that first term on the RHS in the last equation?
no
look at the second picture I sent at the bottom
$\left(\int _0^s:f:''\left(t\right)dt\right)\cdot :s$
Riemann Zeta Male
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anyone know how i can use change of var for 4b)?
You are
@jade hinge Has your question been resolved?
oh ok but how do u do that, cuz dont u need change of var first
cuz ftc has a constant lower bound
FTC2 might be your friend then
This might be a bit dodgy depending on how you've learnt it... but either bound being a variable shouldn't matter...
Oh right it's a theorem
no no go back
FTC1
Like you said, constant lower bound
But there is a theorem you can use to make this not matter
split it into 2?
yes
hm ok i tried that for a while, still cant deal with the individual ones
🤔
cuz u got x-sinx
wait wait wait.
typing
,, \int^{u(x)}_{l(x)}f(x)\dd x=\int^{u(x)}cf(x)\dd x + \int^c{l(x)}g(x)\dd x
So you have this right?
ye
Like I will tell you it won't matter and you don't even need to split like this. You can directly apply FTC2 to variable bounds fine
But this may be a result you haven't seen yet (I'm unsure atm)
@pulsar condor halp
^
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@jade hingereopen
ok
.reopen
✅
yea
that we need exactly this form
uhhhhhhhhhhhh
So what is wrong with just letting
u = sin x
l = x - sin x
and then proceeding
,, \int^{u(x)}_{l(x)}f(t)\dd t=\int^{u(x)}cf(t)\dd t + \int^c{l(x)}g(t)\dd t
Cus we had this.
The upper bound is just u for the left one
the right one, there is a smart trick to do
sure yea, so in the end u have to change the ub from u(x) to x right? to use FTC
whats so special about x though
You can also apply FTC on u being the upper bound
following the exact statement
ah
and as suggested above, the chain rule will do the rest
$I(x):=\int_0^x f(t)\dd{t} \
F(x):=\int_0^{u(x)}f(t)\dd{t}=I(u(x))$
Mosh
forgot about that,..
In the end there is no need to split
its an immediate result you can see
but that depends on what your teacher wants
there is, you can only apply FTC if 1 of the bounds is constant
yea
gotta split
If both are variable
does this not immediately follow
If f(t) is continuous between the bounds
there should be no problems right?
(if it isn't, then yh)
ah
you need to split then apply linearity of the differential operator blahblahblah
ic what u mean ok
but this is a corollary no?
Let me write.
,, \dv x\int^{u(x)}_{l(x)}f(t)\dd t=\dv x\left(F(u(x))-F(l(x))\right)
I'm saying this follows using the above splitting
and is a corollary
(given certain conditions on f)
🤔
sorry i wrote that bad lmao
Well, capital F, I suppose
I meant this
As in as soon as you prove the above, then there is no need to split, surely.
well sure, but your method assumes you can even do the integral
yh ok. something to take care of --- especially when you have something like arcsin(t) as the integrand
so u can set the bound as [-1,1] then
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can i get some help on this
d = 3c+1?
You're looking for a function that looks like C = something
You have the right idea, yup that's oit
So now you can begin constructing a table using the values 1, 2, 3, and 4 as d
Does that look right?
Yup
Make a graph where the X axis is d and the Y axis is C, then plot the points in that table
Like this?
Not quite, that graph is saying that at d = 1, C = 0 but the table says that C = 4
Try graphing y = 3x + 1
There you go
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show how you found the function
why |x - 2|
why √|x - 2|
why |-√|x - 2| + 2|
no you did not, it's not possible to guess it
I mean sure, you did guess it and guessing was the solution but, how did you conclude what you guessed
how did you arrive at your guesses
why is it not x^3 or x^2
why is it not only -√(x - 2)
that's the working out you need to show
note all possible hints, and the inference you got to arrive at your potential guesses
- for example
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you note that f(x - 2) = f(2 - x)
so, you know that this function is even about x = 2
so |x - 2| must be in the function
and so, you only now need to guess what the function is for x > 2, and you'll be done
✅
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how to simplify (9-7i)-(10-6i)
could i get the answer first then the explanation?
The same way we discussed before: add/subtract the terms with and without i separately
If you did (8 - 3i) - (10 + 4i) you would get -2 - 7i
You're done simplifying when you have a number that looks like a + bi
Nope
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Note that that's the answer to my made-up problem, not the one you're trying to solve
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okay i lied i do need help
its $\int _C Re(z) \dd z$
jan Niku (Shuri for Honorable)
along the semi circle radius 4 from z=-4 to z=4
is there a good way to do this that isnt a complete nightmare?
,w integrate ( 4cos(pi/2 - theta)(-4ie^(i(pi/2 - theta)))) from 0 to pi/2
i mean like
this is maybe a horrible idea
could i try to show that $Re(z)$ satisfies CR
jan Niku (Shuri for Honorable)
then just integrate Re(z) from 4 to -4 along the x axis
then take the negative of that result
?
damn
it doesnt satisfy them

.close
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this can be confusing because it's in french
shall we do this in french ?
,rotate
thx
ask in your own channel
stop spamming other people's help channels
<@&268886789983436800>
b&
👨🏻⚖️
yep
du coup c'est quoi w ? Le centre de la rotation ?
pas que ce soit nécessaire pour la b), mais je suis pas sur de comprendre la a)
w n'est pas le centre de rotation
attent je t'envoir la règle
non tu avais raison w est le centre
XDD
Dsl
anyways
utilise ae^i(alpha) = -b et passe en polaire non ?
comme ça ça devient une égalité sur les angles
en fait c'était pas vraiment une question
oh
même si j'ai pas fais les calculs moi même, je vois pas pourquoi ça marcherait pas
attend une minute que je la fais puis je te montre ok?
oui je comprends mtn mais comment je vais faire pour y arriver a avoir alpha
c'était une question ? Tu mets tout en une exponentielle puis tu "passe au log" (mod 2pi) et tu obtiens une équation sur les angles
tu veux dire que je passe en forme trigonometrique?
oui je vois
forme exponentielle, pas trigo
t'es en maths expertes ?
non
prepa ?
bac
spe maths ?
wtf
oui je suis très nulle ;-;
genre bac+2 ?
genre ouais
c'est quelles études ça ?
je suis en dernier année de lycée
donc terminale, pas bac+2
tu me rassures
les marocains sont cools
:)
tu peux faire l'exercice pour que je comprenne mieux ce que tu veux dire
👉👈
2)b)?
pi/6 et -pi/6 si je ne m'abuse
oui c'est vrai mais je sais pas comment lier cetter question avec la 3)b)
e^i(pi/6+alpha) = -e^i(-pi/6)
oooh c'est ça ce que tu voulais dire dès le début
apres on fait quoi
on passe au log?
donc e^i(2pi/6 + alpha - pi) = 1
pi/3 + alpha = pi [2pi], je te laisse conclure
Tu comprends bien le passage entre ces deux lignes n'est ce pas ?
oublie pas le mod 2pi
oui j'ai compris merci infiniment c:
a oui
On dirait que mon égalité est fausse vu que le résultat est faux
non c'est vrai
le resultat est vrai
tu remarqueras que t'a fais pi-pi/3 = -2pi/3. Le - est pas sensé tomber du ciel
?
0 = -2pi/3
A OUI
a = racine de 3 e^(5pi/6)
désolé
non c'est pas grave t'exuse pas
oui c'est bon
je suis très heureuse merci bcp bcp
tu sais faire les c) et d) ?
perso je l'aurais calculer directement mais visiblement le but est de ne pas le faire
utilise la a), t'as besoin de rien d'autre
i.e. pas de la 3)b), la 2) est évidemment utile
la méthode attendue (je pense) est de réarranger ces égalités et de passer au module
on calcul module de a puis de w?
arg(a-0/w-0)= arg( conjugué de a -0/w-0)?????
pourquoi arg ? C'est || ici
évidemment avec arg c'est faux car l'un est > 0 et l'autre < 0
lmao
j'abondonne tu peux fermer channel
non attend
juste tu développe, tu réécris (a-w)e^i(alpha) = -w e^i(alpha) et tu passe au module
d'où la d)
en utilisant b=a barre tu obtiens l'autre égalité à |w|
tu prend le module de chaque coté. Les exponentielles imaginaires ont pour module 1 donc elles disparaissent
la notation du module est la même que celle de la valeur absolue pour une raison
|a-w|= |w|
:)
ça fais 3 mois que j'ai pas touché le math
j'ai mes.raisons
;-;
je sais pas où ça mène je t'avouerais
mais pour la c) il n'y en a pas besoin
tu fais juste ça sur la 2e égalité pour obtenir un résultat similaire, et tu les combine
(b-w)e^i(alpha)=-we^i(alpha)
réfléchis un peu. La même méthode, pas la même expression
réarranger puis passer au module et simplifier
j'ai utilisé la même methode ce qui differencie des deux c'est a barre non?
ce ne serait pas la meme chose? just a barre serait b?
cf question 2) oui
bah
je te l'avais déjà dis
j'ai pas compris ce que tu veux dire
du coup on a les égalités des questions c) et d)
j'admire ta patience
oui c'est vrai
d c'est confirmé
mais c
les deux sont égaux à |w|
et comment on fait pour montrer que w=-1
c'est le cas
passe à la définition avec la racine. C'est une équation de degré 2 (le signe de w est évident)
je vois tu peux fermer mtn
mon .close est sans effet ici.
c'est le demandeur qui peut fermer (ou les modos)
où le bot dans longtemps
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de rien
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what does {a, b E(euro) R & a +/- bi} mean
Send a picture if you can - I can't easily understand that
Euro
Euro
I get that part, but what does a+/-bi mean
I actually have no clue lol. That's not standard
It means z and/or conj(z)
I think it wants a and b where a and b are the components of the imaginary number
what does that mean
no wait they wrote that weird
it's only half of a boolean
there needs to be an equal sign
a+-bi is what?
So there are complex solutions for a, but the a ∈ R makes me think you shouldn't include them
no it's saying that a,b are real numbers
but a+-bi on its own is not a boolean you can't evaluate it to be true or false
@foggy python Has your question been resolved?
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draw
I did
Let G' = g
what I understood from this question was basically that you're trying to prove that if you have some function g(x) that is being integrated from a to b that would be equal to the integral of the midpoint of a to b and then g(a+b-x) is sort of "counting the area" backwards from b to the midpoint if that makes any sense.
I can show u my drawing but it’s on my iPad
And I’m in bed rn
$\int_{a}^{\frac{a+b}{2}} g(x)dx + \int_{\frac{a+b}{2}}^b g(x)dx$
Riemann Zeta Male
Why would you ask ME
oh nvm u said u drew it
💤
idk i havent actually done the Q
I can see that it almost certainly can be solved from the geometry involved, that is all.
Let G'(x) = g(x) then just write out the definite integral
@lean otter Has your question been resolved?
Idk how this helps
@lean otter Has your question been resolved?
Just make a substitution on the right integral and you're done. The information is in the limits
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Hello? Anybody know how to factor trinomials?
Wait so
Wait i mightve learned a tad bit different than that
having a memory problem rn
but i remember my teacher doing it like 2(x^4 - 10x^2 - 39)? And then doing something from there
wait sorry that was the product
just the equation divided by the GCF then do something else after thst
my bad im talking too much
oh yeah
ummm
so 39 has factors 13 and 3
so they are potential solutions to x^4 - 10x^2 - 39
no no
ohh
just let x=13 and x=3 and see if x^4 - 10x^2 - 39 = 0
if x^4 - 10x^2 - 39 = 0 then x=a is a soln, so x-a is a factor of x^4 - 10x^2 - 39
and you can do polynomial division to factorise it
OHH
Bruh sameee but I want to make use of my brain because I cant sleep
and i got a lot of missing math
yeah same, well good luck, do try and get some rest though it's hard to think when you're exhausted
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So
Riemann Zeta Male
@lean otter Has your question been resolved?
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Help me please I need to see if this is right angle triangle or not
Post the image with your first message
@ruby cloak Has your question been resolved?
Is a not a right angle triangle
<@&286206848099549185>
@plucky elk
@queen parcel
@upper folio
Don't ping random people.
If you read #❓how-to-get-help
Dude bro I literally applied for help
Wym you "applied"?
Yes
Lol
Please see if what I did is correct
What have you tried?
This
You haven't tried anything
Is a not the right angle
Read this: • Show your work, and if possible, explain where you are stuck.
I know what it's asking. I'm reading what you're saying. You're not reading what's sent right above your message for help
Why do you think it's A?
First of all it’s a ablisque
Second of all it’s acture
Acute
It has a weird slope so it makes it an oblique
Am I correct
How do you define "weird"?
It’s not constant
"weird" doesn't give any information
It’s not constant
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Slope is constant along a side length
What the answe r
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$I_n=\int {-1}^0x^n\sqrt{1+x}dx:for:n=0,1,2,3...,:show:that:I_n=-\frac{2n}{2n+3}I{n-1}:for:n=1,2,3,....:$
Hamburglers
my first step was
Hamburglers
then by parts
Hamburglers
then did some rearranging and not getting original integral
I let x=sin^2(t)-1 t from 0 to π/2, so it became (-cos^2(t))^nsin(t)dt= (-u^2)^ndu u from 0 to 1, the result I got (-1)^n/(2n+1). Is there something wrong so far?
So eventually I_n=(-1)^n/(2n+1) so I_n=-(2n-1)/(2n+1)I_ (n-1)
(2n-1)/(2n+1) which isn’t 2n/(2n+3) but I can’t find my error 😂
@cerulean wadi Has your question been resolved?
@cerulean wadi Has your question been resolved?
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hey uh
hi
is this occupied
i'm wondering how to solve equations like
i'm not sure what to do with the denominator or the numerator in these situations. Any help is appreciated :]
ok
$\qed$
The Fractalogist
@compact needle Has your question been resolved?
hmmmm yes
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you guys do physics grade 9 ?
just send the question
hold on
i think this is math server not physics
i mean the subjects are closely related tho
So you can't lose by sending the question. If nobody wants to attempt, then nobody wants to attempt.
You can definitely be more on topic with the physics server in #old-network though.
i dont think we should post it i am new so i will go with the flow ig
But yeah, especially at that level, math and physics are pretty similar
newtons law of gravitation
F=GMm/r^2
just sub the values in and you get the answer
yea I did that but I don't get the answer the answer is 3.6 x 10 raised to the power of 22
if you sub it in correctly you will get the right answer, check your terms
the question gave it in the correct units as well so theres no need to convert it
I assume you have a calculator? You don't need to carry this out manually
just punch the values into a calculator from the first step
The E button is very helpful for these
well calculator not allowed sadly
Indian problems
you cant do harder gravitation questions without calculator though
yea am in 9th grade
yea i got my calculator in the 5th grade
anyways your first step is right so just check your arithmetic
no way im doing that without calculator, its a waste of time imo
true
questions should test your concepts, not how well you can do powers of 10 in your head
I got the concept down in an hour but been doing this for last 5 hours and still haven't got how to do this life kinda sad when country dont allow calculator sad
yeah that is just really odd
this goes till grade 10th
i have no idea how you would move on to harder gravitation questions like this
you will have formulas like T=sqrt((4pi^2 r^3)/GM)
where r G and M are really huge/small numbers which are in multiple magnitudes of 10
so
we just use exponents for that and write it like that
for now
like from eleventh grade we get calculator
cuz thats just inhuman
this is news to me, i never knew a country which disallows calculator for physics, and gravitation specifically
well without a calculator theres only so much you can do with the formulas so it really limits what you can learn
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Need help with c I don’t understand where the points a b and c and d are
I don’t know how to use what they give to get a rough shape of the quadrilateral and bame it
Nvm I just made a = 1 and b is 2 and drew it out
Can someone confirm if this correct and I didn’t do soemthing random
@rich badge Has your question been resolved?
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,rccw
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fourier transformation
i did it with changing cosx to ((e^ik+e^(-ik))/2
doing that i will get 2 integrals and the final answer will be sin(2k)/2
but its wrong idk why
i think actuall solution is done with integral by parts then forming the exponential terms into trigonometric terms and with calculator i get sin(1-k)/(1-k)-(sin(1+k)/(1+k)
theres a hint that says use product rule of fourier transformations, idk what that is
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@lean otter Has your question been resolved?
can you zoom in its hard 2 read
thx
reading
ok is ur picture right do you think
have you done part a
surface area of a cone is
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struggling with this integral
i can think of a way to express it in terms of a gamma function
but to get an exact answer would be quite difficult by hand
when i plug it into an integral calculator i get an erfi function
and i have no fucking idea what that is and i dont think thats what my professor is looking for
ive tried that. I tried subbing u = x^500, so du = 500x^499 dx
or including the negative in that usub
so i get either e^u^2 du or e^-u^2 du
Shen
i can see lol
Times some constant
yeah
Because x^499 dx ≠ du
yeah youre right i just dropped the constant for the moment to worry about the integral
Ye
Im not quite sure how to evaluate this new integral by hand if im being completely honest
You can't using just single-variable calculus
e^(-x^2) has a non-elementary antiderivative
Have you heard of the Gaussian integral?
im familar
It uses that integral in here
im about to say something that might be completely wrong so bear with me
This looks like a useful identity. Since the bounds are 0 ----> Infinity and this is an even function, can i say that the final result for that would be sqrt(pi)/2?
I'm impressed you got that
Not gonna lie
But you couldn't be more correct
Yup
oh alright cool, thanks a lot for your help
np np
Dividing by the 500 from the u-sub gets you:
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hi, I'm trying to do the mean of excel cells with this formula =B2:M9/36 but i get a value error ! i dont understand
=AVERAGE
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I need help w circle theorem
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Can you guys help ?
@native pagoda Has your question been resolved?
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For 2a) is it (P(sick female) + P(sick male))/ (P(sick female) + P(sick male)+(P(healthy female) + P(healthy male))
so (0.5+0.003)/(0.5+0.003+31.8+30.3)
anyone here did CEMC grade 11 contest ready to discusss?
ready to discuss all 25 questions for checking
@solid vigil Has your question been resolved?
P(X=f_s)=p_11
which part are you stuck on?
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i have a question (combinatorics)
we have a ticket from 000000 to 999999
if the sum of the first 3 digits is equal to the sum of the latter 3 digits, it would be a lucky token
if the sum of all digits is 27, it would be a good token
now, which one has more ticket, and find the difference of amount of both ticket
they said to use bijection, but i do not understand lol
For every lucky token, you can assign a three digit number. Likewise, for every three digit number, you can assign a lucky token. See how?
uhh i kinda get it, but what kind of 3 digit number tho
@still acorn Has your question been resolved?
<@&286206848099549185>
@still acorn Has your question been resolved?
<@&286206848099549185>
Same many
There are two maps, f from lucky tokens to three digit numbers, g from good tokens to three digit numbers. f(abcdef)=abc, g(abcdef)=abc. For example f(084715)=084, g((769320)=769
Notice that f and g are surjective
So the number of lucky tokens is $$|\cup_{m} f^{-1} (m)|=\sum_{m} |f^{-1} (m)|$$
Similarly the number of good tokens is $$|\cup_{m} g^{-1}(m)|=\sum_{m} |g^{-1}(m)|$$
Now for any three digit number m, |f^-1(m)|=|g^-1(m’)|
Where for any m=abc, m’=(9-a)(9-b)(9-c) for example (472)’=527 so |f^-1(472)|=|g^-1(527)|
So when you take sum, you can pair m and m’, |f^-1(m)|+|f^-1(m’)|=|g^-1(m’)|+|g^-1(m)|
Therefore they are equal
(Where m=m’ |f^-1(m)|=|g^-1(m)|, when m doesn’t equal m’ you pair m and m’ that’s what I meant )
where is 9-a, 9-b, 9-c from
I thought you could figure it out yourself…
oh damnnnn
For a three digit number m, I use S(m) to denote the sum of three digits, for example S(042)=6
Then (m,n) from f^-1(m) iff S(n)=S(m)
Like (024 312) from f^-1(024) because S(024)=6=S(312)
On the other hand, (m,n) from g^-1(m) iff S(m)+S(n)=27
But 27-S(m)=S(m’) right
So iff S(n)=S(m’)
So (m,n) from g^-1(m) iff (m’ n) from f^-1(m’)
Where m=100a+10b+c then m’=100(9-a)+10(9-b)+(9-c)
You can easily see that S(m)+S(m’)=27
alright lol
thanks for your help, this really meant to me, now I am still stucking a lot with bijection problems
Sure just ask, when you can’t figure out
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@young moon Has your question been resolved?
lemme try it'll take time but yeah wait
you still need the solution or is it solved?'
That’s not how trigonometric manipulation works, have you learnt double angle formulae
angle can not be added there is separate formula for it
you need to understand the graph
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As x approaches a, do i just write infinity? +- infinity? Or just simply does not exist?
From left, right and both sides.
Wdym, there's no graph of a function here
That's also why I'm confused. That's the question, so i just write does not exist for everything?
Of a well-defined function at least
The function is only defined on x = a so f(x-a) does not exist
And if this is the graph, then it looks like it's not even defined around a
So the limit wouldn't exist
also f(x) is not a function at all bc it fails the vertical line test
pretty badly
ITs a relation and a relation defined on a single point
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can someone check over my work here?
Seems right to me
sorry, i don't understand the graph
could you explain what im looking at and how it shows that the question is correct?
I mapped the term as points and now you see that when d =10/3 (I used d instead of x) the points line up
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Please can someone check this question for me? I think I have done it wrong
yeah i got that when i used wolfram too, but it has confused me as its not the same as my answer
pls help!
oh wait am I being dumb
Why is your integral sign remaining after the fact
Your 3rd line onward does not make sense
Write it properly
ohhh
Write the dx for the first two lines too
right!
Before you integrate, you need that thing, along with dx
It tells readers what you are integrating with respect to
okay! wait on sec, I'm just writing it
so after the 3rd line, it doesn't make sense?
What should I do after the (1/2) (5-3x)^-2?
oh sorry, did you mean after (1/2) (5-3x)^-3?
Yes
So how should I do it? 🙂
$$\begin{aligned}&\int\frac{1}{2\left(5-3x\right)^{3}}\dd{x}\=&\frac{1}{2}\int\left(5-3x\right)^{-3}\dd{x}\=&\frac{1}{2}\left(-\frac{1}{3}\right)\left(-\frac{1}{2}\left(5-3x\right)^{-2}\right) + C\
=&\frac{1}{12\left(5-3x\right)^{2}}+C\end{aligned}$$
pepper
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submit it and find out 
no it has ended ald
what
and it wont show the answer coz is final
it won't show the answer because it's a test?
no coz it is final exam
<@&268886789983436800>
final exam they wont show results
that's unfortunate
the exam is ald over
why are u tagging moderator loll
im just trying to know if i have done it right
moderator here. you;re; in big trouble mister

Closed due to the original message being deleted
so you can still see your answers on the screen? your buddy also posted a question in #help-8
and it doesn't look like it's over for them
not sure why u r creating trouble @ancient escarp
They are just following the rules
because academic dishonesty isn't tolerated
And your post is a bit sus
sorry for that
i find it very weird that 3 ppl post the same q at the same time
you can also edit anything on html pages 
sure but i tend to give benefit of the doubt when it comes to that lvl of manipulation
it's already closed since you deleted your original message
speaking of deleted messages, i was talking about editing the text on the screenshot you sent and now deleted, not your computer time
Lets just drop it
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Shouldn’t the answer for this question be 2(3 root 5 divided by 5) or am I wrong?
it is
