#help-43
1 messages · Page 67 of 1
z1 with z2?
mango
you know both of them
mango
or $3 + 2i = 5i$
mango
it's the same reason why you can't add integers with square roots for example
well you can but like
not in the sense of $3 + \sqrt{2} = \sqrt{5}$
mango
so how do multiply them
so i just write these 2 down?
okay finally
what do you have
what do you mean by that
like
replacing z_1 and z_2 with those numbers is enough, but it really depends if your teacher is kind or not
you might be required to simplify that too
and i think that you're required to simplify it, since you do get a nice answer
its okay for now, seriously thank you very much tho. I will aslo ask the teacher for some help in advance i have 1 week to study but i cam here early purely because i dont understand SHIT about maths. and a lot of people say its very easy and im upset because i cant solve this shit
no problem, just make sure to study at least 1-2 hours a day
i still have 3 more others to learn in advance so i think im calling it quits for tonight i will start early tommorow and ask for help and maybe i have more energy
yeah no i think i can learn it in here to be honest, i tried chatgpt but didnt work but
in here people really have the nerves to help you out
and i couldn't be more thankful
yea chatgpt sucks
Thank you for your time, means a lot
no problem, good luck on your test
see you later in advance thanks to everyone here who tried helping 😄
how do i close this
so people can take the channel
do .close
.close
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I am struggling on the definition of a product topology, it says that the product topology is defined by the basis B = {U x V | U and V are open sets respsectively in X and Y}
I feel like there should be more resriction on what U and V can be
If i take U and V just to include one element of X and Y wouldnt this be different to taking a different open set of X and Y which have more elements??
what do you mean by taking U and V to only include 1 element?
you don't know that 1 element sets are open
If i had (X,T)={∅,{a},{a,b},{a,b,c},X} and (Y,T)={∅,{1},{1,2},Y}
to be open in a topology just means that the set in the topology right so, wouldnt {a} be a valid open set and i could choose {1} to be an open subset of Y.
Then the product of these two would be quite smaller than if i picked a different set
Wait so is the product topology defined uniquely based on the U and V I pick?
That’s what I don’t get
wdym pick?
Like in the definition it makes me think that there is a U and V I pick from X and Y then that creates the basis for th product topology
Or is for Ui and Vi subsets of X and Y
B = {U x V | U and V are open sets respsectively in X and Y}
B is the set of all U x V where U and V are open sets of X and Y respectively
Okay I’m stupid
where is Ui and Vi coming from
I thought we were picking a unique set to generate it
Like Ui and Vi are all the subsets of X and Y
why is it indexed 
but like where is the index coming from
No where just typed it
ok so it shouldn't be indexed then
Alright
you take U an open set of X, V and open set of Y, then you declare U x V to be open in X x Y
Ok
letting U and V vary, all these product sets U x V are open in X x Y
the topology is generated by them
if $W \subsete X \times Y$, then there exist $\UU \subsete T_X$ and $\VV \subsete T_Y$ such that [ W = \Union_{U \in \UU, V \in \VV} U \times V ]
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how to solve this chat?
What have you tried?
nothing i need to know the proper way to solve
bcs usually i just combine the x and add the exponents but theyre negative this time
so im wondering whats the right way to combine
if the negative is fazing you, can you handle the 6?
if you can handle the 6, how would you do it?
its the exact same way! in-fact, if the negatives are bothering you, you can just cancel them out in this case!
okay makes sense i was just trying to make sure i was doing it correct
you do realize that its -x^2 multiplied by -x^5 and thus its like multiplying -1 * -1 * x^2 * x^5
because multiplication is... what's the word
assicoacoateivive?
anyways yeah you can move the negative around terms that are multiplied
-2 * 3 = 2 * -3
(associativity has to do with rebracketing. you're looking for commutativity.)
so 6x^10?
wonderful! ty for correcting me
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is this logic correct?
cuz they didnt show me how to do this type of equation so i wanna make sure its right before i do all the others
No it doesn't work like that.
okay how do i solve it
no, since since a and 1 are not of the same base you cannot use that rule
In order to use those rules you need to have the same base.
There's nothing to really "solve" honestly.
Dividing by 1 doesn't do anything.
So you just have $2a^{-3}$.
Ho-Oh's rainbow
i also have this equation
But then for any negative exponent, you are always allowed to make it a positive number by simply moving it to the denominator.
so thats what i mean how do i solve this type
So you get $\frac{2}{a^3}$.
Ho-Oh's rainbow
okay i see
Same idea, anytime you see a negative exponent, you can always flip it and change the sign.
so like this
Since the negative exponent is on the numerator, you can move the power to the denominator instead.
Yeah exactly!
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back again lmao what does it mean by degree cuz it gives me the answers but half of them dont make sense to me
do you still need assistance?
yes
no i havent
the degree of the polynomial is the highest power of the variable present.
okay so how is 7’s degree 4 is it bcs its one term and each exponent together equals 4?
yes. that middle term has a degree of 4 because x contributes 3 and y contributes 1.
so the whole poly has a degree of 4.
no worries. anything else?
nope ty!
all the best then!
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Hints!!
which one
i dont know the name but u need to use that theorem about areas of triangles
that tell you about their ratio of areas
there is one question only
[abc] here is area triangle u mean?
6 ratio by median?
If 2 triangles have the same "height"
then their areas will have the same ratio as their "bases"
In parallel lines?
is this familiar?
uhhh no..
maybe someone else can explain / get the name of this theorem
dont think that theorem have a name
but anyways, if A = 1/2bh then A1/A2 also cant be found if same height anyways
if you draw a random triangle XYZ
then on the line YZ you put W somewhere in the middle
Then [ XYZ ] : [ XYW ]
is equal to
YZ : YW
Well, I'd first use Menelaus to find EF/FB and then use the equal-base-unequal-heights thing. If that's not in your syllabus, well then use similarity ig.
In which triangle should I use menelaus?
that is not thales
?
there arent that many triangles to try 🥺
For ABE~
AC/EC.AD/DB.BF/FE=1
(AC.AD.BF)=EC.DB.FE
5.1.BF=4.3.FE
BF/FE=12/5
What next?
@dull moon
Base is BC
And we have BFC area
12~144 so 17×12
ABC area
@dense mason
Please check
Same height how?
*its the same height)
its just the length of the perpendicualr dropped from C onto EB, for both cases
How can you say it is perpendicular?
Are you saying CF is same for BFC and CFE triangle and base is different
BF and FE base
CFE area would be then 5.12=60
@dull moon
Yeah i didnt understand this part also
no no im not saying its perpendicular
Ok let's construct a perpendicular from C onto EB. call this CX
then the area of $CFE = \frac{1}{2}EF\cdot CX$
Annie Maqionde
and that of $CFB = \frac{1}{2}FB\cdot CX$
Annie Maqionde
so $\frac{CFE}{CFB} = \frac{EF}{FC}$, is it not?
Annie Maqionde
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<@&268886789983436800>
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how do i do this q??
idk where to start
cut the belt up into circular pieces and straight line pieces
to do that, you first gotta figure out where on the wheels the curve becomes straight
find that by doing this:
<@&268886789983436800> weird username
Thx for notifying us. But it was deemed to be fine.
then:
to help is this new red line drawn, parallel to the outer blue one
figure out the length of that red line first
then its the same as the blue part
that will figure out the straight line piece
for the curved pieces, youll first need this green angle:
that way, you can find the purple angle for the arc
think and it will be true: this other arc is two green angles (use parallel lines to prove this)
with that, you just have to figure out the numbers in order then add the pieces together
go ask if youre stuck, this is just the general process
maybe it makes more sense when you put numbers to things
@royal furnace Has your question been resolved?
ohh
oh so we use tangent in this case
ye i get it but how do u even think of that
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right I wasnt sure how to explain that
is this just lots of practice
no
oh
practice isnt going to tell you what that angle is
no i mean like making the rectangle
well first you still gotta trust that its a right angle in the first place
cuz i labeled it i got tangent and stuff but i didnt know what to do after that
is that intuitive for you
uh idk
alr lets consider that first
wdym
ye i know thats right angle cuz of tangent rule
what told you its a tangent then
because u made it a tangent?
you cant cite me as a source for the problem yk
cmon a real reason
I drew that because it wasnt obvious
oh its tangent cuz it touches the circle once
no but i drew that already as well
like i knew that was tangent angle bu ti didnt know what to do from there which u did the rectangles
we need to do that
yea up next is that
but doesnt that go into circle proofs
that one I dont exactly know how to introduce
for this, heres something you can consider
we essentially have a shape thats like this:
ye cuz i didnt recognise it
but you draw enough lines and you make the connection
you figure that out, you get the lines
hmm ic
as for the green angles, you know how to get those?
no theres something more direct you can just do here
sine cos tan?
ye
so you identify a trig ratio on the right triangle here
then you arcsin, arccos, or arctan it (choose the correct one based on the sides youre dividing for the ratio) to get the green angle
wait so after finding green we double it then do either 360- that or 2pi- that right
yep
nice
yep
alr then i get it now
ty for ur help
the sine and cosine rule would just be more longwinded versions of this
dont forget that you can use them directly, just for this case
hm ye cuz this is right angle triangle
yep
np
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Can someone explain transformations of graphs, on how to solve questions like this? How do you know by what scale it's being transformed?
Thats right
it compressed leftside thats all i can notice
and how do you move a graph to the left?
f(x+c) I think?
yes
but how to know how much compressed? and how to move
now here I think a square is displacement of 1?
yes
that's what I think is compression
how doyou know
is it not move left 3
nope its compressed
it's move left 3 then compressed, you can't get the transformation simply by compressing
I dont think it moves, initial left point stays at the same spot
you compare the graphs, for example, for the linear part of f(x) on the left, it moves right by 3 units, but for the linear part of g(x) on the left, it moves right by 1.5 units
scaling starts from x = 0 though?
if you only think about the linear part from y=-x-2 it becomes after the transformation -2x+5
what are you tryna say
but when you compress a graph, it doesn't start from that initial left point, so there is definitely translation
which then applying the same to the linear part on the right becomes different
note that this is compressed horizontally, not shifting
perhaps you can find dilation factors
how is it different..
there are 2 types of dilation factors: from x-axis, and from y-axis
g(x) = f(2x+3) or am I missing something
wrong
g(x) doesnt shift
since the left-most point still remain the same, seems like it has been "squished"
no but it literally does..
then explain the point (-3,1)?
does it move?
and if you say g(x) is f(x) shifted, then all of the points must also shift with the same constant unit
plug -3 into g(x) = f(2x+3)
you dont really understand here right?
all i understand is that a compression would look like this
which must then be shifted
so like wdym it's only compression 😭
compression starts from x = 0
so you can't compress from (-3, 1)
or in my case i moved 3 first, then compressed it but either way works
It doesn't move because it coincidentally overlaps
I see
I mean it does move
Just ends up at the same place
But it cant move that much for 3 units
1.5
2x + 3, 2*(x + 1.5)
@pine cloak Has your question been resolved?
@pine cloak what do you still not understand
i got it now...
wahts the final answer
i can't tell you that directly
seeing how much y changes
the red line is y=-x-2 right?
which in the new graph is translated horizontally to the right by +1.5
so f(x+1.5)
y=-(x+1.5)-2
ok so far?
@pine cloak
yea
but now
look
and
in g(x) at x=-3 y is 1, while at our current point it is not
so we have y=-(x+1.5)-2 after the traslation
and therefore assuming that at x=-3 the function is equal to 1 then you have
so we need to find the new slope
that comparing the points from before and after (-3,1) and (-1.5,-2) m=(-2-1)/((-1.5)-(-3))=2
so the new line is y=-2(x+1.5)-2
so you acted on f like this
f(x+1.5)
and the f(2(x+1.5)) = f(2x+3) = g(x)
@pine cloak Has your question been resolved?
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where do I go from here
Let x be Andy candies
Then we have ratio 1:6:14, so what is candy of luke and tina in term of x?
Using x would be easier to imagine of
x:6x:14x I think
Correct
If Tina gives away 3/7 candies, then what is the number of candy being given away interm of x?
14x
wwould I do 3/7 X 14 which is 6
So the candy give away is 3/7*14x, right?
Correct!
So 6x here go from Tina to Andy, but Andy have x candy, then number of candy Andy have is?
6?
oh shit 7x lmao
So if tina give away 6x candy, what does she have left?
if she has 6x candy and given away is that not 0?
oh 8x then
she gives away 12(1/2)% of the rest, what percentage this is?
12.5%
The rest is 8x candy? Then she gives away how much candy?
Okay so Tina was left over with 8x candies after giving away some to Andy right?
yes
Now the question says that she further gives 12.5% of her remaining candies to Luke
So what did shw give to luke?
ok so would I do 8x X 12.5 or do I divide it
Multiply it by 12.5/100
Since it is percentage
Multiply!
i got 1 as the answer
Correct
This means 1x
She gave this to Luke, which originally have 6x
How much he have now? How much Tina have left?
This 1x candy was given to luke by tina as minhh said
So tina has 1x less candy now right?
ye bc it has to add to 21x I think
Who receive the 6x
andy
What candy that andy have initially?
1x
How much was given to Andy?
6x so he would have 7x in total
Okay good!
btw
For the second time, how much tina give away
Tina had 14x gave 6x to Andy so he has 7x in total so that leaves tina with 8x
then she gives 1x to Luke
Okay, thats after the first giveaway!
Yup!!
Thats the second giveaway
so she has 7x left over
Now you tell me, how much do all three have finally?
Andy has 7x Luke has 7x and tina has 7x as well
im not sure if it answers the question ill check the mark scheme give me a sec
Why not?
The question asked was if Tina was right at the end, aka all three having the same number of candies
yes thats the answer thank you
And you did find that at the end, all three did have the same number of candies!!
Your welcome !!
It asked if the statement is correct
holy shit thank you @dense mason and @sleek meadow u 2 dealt with bs lmao
Good luck for your exam buddy
thank you
yes but im gonna need to keep this open to answer the question on a pdf since i need to show it to my tutor
Np buddy
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What even is this significance of C in this Question?
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What good is calculus anyway, what does it have to do with the real world?! Well, a lot, actually. Optimization is a perfect example! If you want to figure out how to maximize your profits or minimize your costs, or if you want to maximize an area or minimize a distance, you are finding the maxima and minima of a function, and that's doing calcu...
In the surface area problem
its asking for the minimum
what if its asking for the maximum? what are the tweaks?
I still don't understand because the general process seems to be the same for me
the only thing you need to do is to pretty much create a general equation (or use equations depending on what is given), derive then equate to 0
the problem im having is what to do to specifically find maxima or minima
If anything you could check the sign of the second derivative and this will tell you whether it's a maximum or a minimum.
In general though, depending on the constraints, you may not be guaranteed the existence of a maximum and a minimum
yeah, but the thing is the general steps feel loosely the same
so i might feel like im doing something correct but the second deriv test says otherwise
Yes, they are the same. You find critical values and then classify them.
pretty much, cause optimization is basically in concept just finding local maxima/minima depending on whats gien
given
The wording of the problem and the information you're given will usually ensure whatever (min or max) you're looking for exists
i see
And again, in general the problem may be posed in such a way that talking about a maximum in the same context doesn't make sense.
For the surface are for instance, there is not maximum in the problem given in the video
but what if i have a problem and its asking me to find both the maxima and minima instead of one or the other?
like this one for example
Then you may just find critical values and check whether they are maxima or minima using the second derivative.
right right, they can contain multiple critical values
so if one of them can indicate a maxima, the other can indicate minima
i gotchu
Yeah, if they ask for both, generally, you would expect them to be different critical values
Unless the function is constant or something
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How do I factor $x^2-2yx-24y^2$?
Vortac
What do you mean?
when you have a polynomial ax²+bx+c, its discriminant D is b²-4ac
and its roots are (-b +- sqrt(D))/2a
here you have b = -2y and c = -24y²
so D is 4y²+96y² = 100y²
the roots are (-2y+-10y)/2
so -6y and 4y
isn't it yx though?
well I just told you to treat it as a polynomial in x
so the coeff are 1, -2y, and -24y² in this order
but I thought coefficients just include the numbers?
well isnt -2y also a number
coefficients need not be constants if that what you mean
this is what I meant
@echo thorn Has your question been resolved?
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struggling on where to start here
i just learned about the L operation, linear independent solutions / homogenous solutions, but i wasnt taught how to find the particular or homogenous solutions myself
you solve homogeneous second order constant coefficient differential equations with the characteristic polynomial, see here: https://tutorial.math.lamar.edu/Classes/DE/SecondOrderConcepts.aspx
and for more in-depth treatment of the cases you encounter:
https://tutorial.math.lamar.edu/Classes/DE/RealRoots.aspx
https://tutorial.math.lamar.edu/Classes/DE/ComplexRoots.aspx
https://tutorial.math.lamar.edu/Classes/DE/RepeatedRoots.aspx
In this section give an in depth discussion on the process used to solve homogeneous, linear, second order differential equations, ay'' + by' + cy = 0. We derive the characteristic polynomial and discuss how the Principle of Superposition is used to get the general solution.
In this section we discuss the solution to homogeneous, linear, second order differential equations, ay'' + by' + c = 0, in which the roots of the characteristic polynomial, ar^2 + br + c = 0, are real distinct roots.
In this section we discuss the solution to homogeneous, linear, second order differential equations, ay'' + by' + c = 0, in which the roots of the characteristic polynomial, ar^2 + br + c = 0, are complex roots. We will also derive from the complex roots the standard solution that is typically used in this case that will not involve complex num...
In this section we discuss the solution to homogeneous, linear, second order differential equations, ay'' + by' + c = 0, in which the roots of the characteristic polynomial, ar^2 + br + c = 0, are repeated, i.e. double, roots. We will use reduction of order to derive the second solution needed to get a general solution in this case.
why do people just assume everyone knows/can digest more complex math notations
this is not as helpful to a new learner as you would think
lmao what
i will review the provided materials and then depending on such a thing i will join in this argument for or against you
one moment
someone new to math isn't going to get what you just conveyed
doesnt mean it's harmful, what's your point?
the whole skill in teaching people is letting them grasp concepts without using notation
If OP has questions they can ask
i think maybe we should have this conversation in #「helpers-lounge」 and keep the channel focused on the help
thanks! very helpful, i will certainly be back to ask you abojt nonhomogenous equations as well
but for now that’s all
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another channel i dont have acess to
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i don't quite understand this definition
It’s a property. It means that the vectors of F are exactly those vectors that get mapped to themselves under the projection
Or like p(x)=x
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is this a correct proof by contradiction
In the first case why is x or y congruent to 0 mod 4?
the product is to be congruent to 0
to either one of them should be congruent to 0 to do that
we could also have both of them be equal to 2 mod 4
but we reject that cuz we assumed that x is not equal to y
x = y = 2(mod 4) doesnt mean x =y
like take x = 6 and y = 10
ohhh right
mod 7 ?
especially considering that x and y are bounded by (p-1)/2
maybe work mod p
expand this and some terms will cancel mod p you get some congruences work with that
i just get
(xy)² = k² (modp)
so xy = +- k (modp)
i guess you could write k = axy + mp where a is {-1,1}
and sub back
this is not easy
idk
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Why is da and E parallel?
dA points outward because it is always normal to the surface, E points outward for this case because of the spherical symmetry
@hexed copper Has your question been resolved?
Why does that look like- uh nvm
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I NEED HELP WITH CALCULUS III HOMEWORK BRO PLZ I DONT UNDERSTAMND TJOIS
I might be able to help, can you like post a problem?
i need help like starting these problems like i have no idea what to do i know i ahve to figure out if it converges or diverges but i lowkey forgot
i dont know how to be rigorous about it
but i can tell which converge and diverge
yeah im barely starting and i already need help wait how can u tell thoooo
ok so
i know it sounds silly
but i think of a wall
and im standing a bit away from it
now someone tells you to take a step equal to half the distance to the wall
and so you do
they tell you to do it again, but now the diatance changed
sinceyou are closer to the wall
but if they told you to take twice the distance
then you would pass the wall -> diverge
if you take portions of the distance, smaller than it
-> converge
as long as the steps are smaller than 100% of the distance you will get closer to the wall
bur never reach it
but*
How is this relevant to your problems?
The idea sort of works for 89, 90, 91
let n+1000=k, if n=1, k=1001, so you can rewrite it as summationfrom k=1001 to infnity of 1/k(you can also use this for 88), you can then apply basic calc knowledge to know this is approximately lninf-ln1001 which just tells us divergenceif
worksfor 92 as well
so 87 and 88 both diverge then right
OOOOO
okay
i can make n =1001 and then it turns into 1/n
and that diverges
and i can do the same for second one n=1+10^80
series in the form summation from k=0 to inf ar^k converges if |r|<1, because fractions get infinitesimally smaller,,, their task now is to express it as a series first
this works for 89 to 91, 92 is a bit more trivial but you can express it as the summation of (1-sqrt(pi/3)) * (find this one)^2n from n=0 to +inf,
yes
yeah sry like i said im not rigorous at all sry to poster if I just confused you
@crisp fossil express the series in 89-92 as summations in the form ar^k
where a is a constant(usually the starting term) and r is how much you multiply to it each time
I can't really say much abt this I only started studying about this recently
oshit yes
i get what you are saying now
yes this is what i meant but you managed to translate my nonsense
and you also make it clear that you can reach SOMETHING
be wary of no 91 btw
for 91 i thought like this
you explained it like gojo explained infinity
I dont know what gojo is but he sounds like a silly guy
(1/2+1/4+1/8+...)x=x, that is only if you reach infinity though
for number 89 isnt it 1/10^n-1 how do i go from thjere like do i
well
r is less than 1
so what does that tell us
^
yes
yeah
thats less than 1
which is?
let me see
be wary of it
91 converges 92 diverges?
yes and are you sure about 92
oh wait yeah ur right
how does 91 converge
no way
Does it? If so I need to revise
i have been wrong before and will be wrong again 🙂
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oh nvm i didnt see the exponents lol
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Let $a>1$ be an integer, Prove that every element of the set [ {a^2+a-1,a^3+a^2-1,...,} ] are pairwise coprime
Copter
i dunno how to do this
i tried compare a^k+1 +a^k -1 and a^l+1 + a^l-1 but that didnt get me anywhere
Xavier 🌺
Clearly $A_n \equiv (-1) \mod a$
Xavier 🌺
Also $A_{n+1} - aA_n = a-1$
Xavier 🌺
Unless I fucked up my calculations
From here you can use Euclid's algorithm to find gcd
@hazy obsidian you with me?
yea
wait, on what😭
sorry i kinda suck
No worries lol
Well you can use the algorithm to show that $gcd(A_m, A_n) = gcd(A_m, A_{m+1})$
Xavier 🌺
(do you see how)
And now it becomes easier cuz you have an explicit formulation for $A_m$ and $A_{m+1}$
Xavier 🌺
ohh cuz you get A_n from it
Ye, you break down the problem from "two arbitrary elements" to "one arbitrary element and its successor"
Id say try and show this first. Then we can move on
(or alternatively if you can continue yourself from here, feel free to)
= (A_n, a-1) and take An mod a-1 = 1
Yup
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I've done v = mu(a)+ lambda(b)
Then I used the condition given and got v.c = 1
How do I solve for both mu and lambda
This question was wrong I think
JEE didn't give bonus for it but you can't find both
What was wrong in it? The same thing I said?
Yes
You can't solve both mu and lambda
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I kinda know what to do but I need help putting it in a clean efficient proof
For the first part it should be relatively straightforward to prove $[x]_n \subset {x + kn : k\in\Z}$ and vice-versa.
Azyrashacorki
What's the described equivalence relation here?
$\mathbb{Z}/n\mathbb{Z}$
arachi
so you would prove two inclusions
I feel it would be appropriate. You would be showing that the representatives of [x]n are exactly those integers of the form x+kn.
Looks right.
You're essentially doing the same thing but both sides at the same time with iffs.
Then the second part arises since the remainder mod n is unique between 0 and n-1 by the division algorithm,
so this is good?
At a quick glance, yes.
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is there any efficient way of doing this
because finding the double partial deriative and then fiding the variance of that ain't pretty
Okay, even once I find the double derivative, the expectation is a function of the sample no?

Like the double derivative wrt sigma^2 is
$\frac{-1}{\sigma^4} - \frac{1}{2} \sigma^6} \sum (x- \mu)^2$
Wai
Compile Error! Click the
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then using the defn of fischer information we get $\frac{1}{\sigma^4} + \frac{ \sum (x_i- \mu)^2}{2 \sigma^6}$
Wai
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Can anyone refresh me on how to do these kinds of system of equations?
I've some more kinda but let's do this first
Here, i got something for you to try
This is a classic factorization problem
@serene coral
So look at the first equation
I plugged in some random big value for $y$, like $100$ here and solve for $x$ (note that this is in a draft)
1 divided by 0 equals Infinity
So when i solve it
it gives -100
Alright
,w solve for x: x^2 + 2*(100)^2 + 300x = 3(x + 100)
1 divided by 0 equals Infinity
Which means you would have a $x + y$ in the factorization of the 1st equation
1 divided by 0 equals Infinity
i can see (x+y) in the rhs
In other words, your first equation could be written into $(x + y)(something) = 0$
1 divided by 0 equals Infinity
That's a guide for you to factor
got it into (x+y)(x+2y-3) = 0
And looking at $x = -197$ tells me that $x = -2y + 3$, because $x$ is $-200 + 3$
1 divided by 0 equals Infinity
Yep
And from that you can substitute each case into the 2nd eq and solve normally
But how about when both equations have square roots in them?
That's for another time
That's a different kind alr
Well I'm revising the advanced part of systems of equations so...
Here your first equation looks like that it can be factored out
So we can try the trick where we substitute y = something and guess the factors
but like i said, what if it looks ugly?
That's a different kind alr
You got any examples about the ugly roots in both equations?
Like most of the time, the solutions to these are ugly numbers, so you gotta pick some good ones from the internet
it's in the book, which i can't snap a pic rn
Aight
Do you notice that when you swap out $x$ and $y$ in the first equation, you get the second one?
1 divided by 0 equals Infinity
yeah i kinda noticed that but didn't know what to get out of it except both roots are swappable
So if you subtract both sides of the equation
You'll get a $x - y$ factor guaranteed
1 divided by 0 equals Infinity
How can you be sure abt that?
Or probably $\sqrt x - \sqrt y$ if the equation is ugly
1 divided by 0 equals Infinity
You will always have a $x = y$ solution when you solve it out
1 divided by 0 equals Infinity
For instance, if $x$ solves out to be something
1 divided by 0 equals Infinity
And if i flipped the 2nd equation to the 1st equation, i can also solve for $y$ the same way i did for $x$
1 divided by 0 equals Infinity
I think this question, there's a $\sqrt x - \sqrt y$ factor
1 divided by 0 equals Infinity
So here, try to expand both sides out
$(1 + x\sqrt{y})^2$ is $x^2y + 2x\sqrt{y} + 1$
WLOG, $(1 + y\sqrt{x})^2$ is $xy^2 + 2y\sqrt{x} + 1$
1 divided by 0 equals Infinity
i got $2(\sqrt{x}-\sqrt{y})(x+\sqrt{xy}+y+11)=0$
Thomas
The first case will always solve out to $x = y$
1 divided by 0 equals Infinity
<@&268886789983436800>
but what about the second?
Usually you would have to prove that there's no pairs satisfy this
So look at this, the systems must have the condition $x, y \geq 0$ right?
1 divided by 0 equals Infinity
So the $LHS \geq 11$, but $RHS = 0$
1 divided by 0 equals Infinity
it doesn't say x, y >= 0
in fact it doesn't give any restriction except x, y are real numbers
But there's $\sqrt{x}$ and $\sqrt{y}$ in the original system
1 divided by 0 equals Infinity
And if either $x$ or $y$ is negative, then the system is invalid
1 divided by 0 equals Infinity
(assuming you're working in reals)
so if the roots are interchangeable then some variation of x-y must be in the final factorization right?
Yep
Something that leads to $x = y$ will be in there
1 divided by 0 equals Infinity
,w solve 2*(1+x sqrt(x))^2 = 9x sqrt(x)
any other tips/tricks that you can pass on?
just practice more you will get the feeling
you will have the observation skill
just look at this system of equation
you will see how symmetrical it is
lead us to the first hypotheses
x=y or x=-y
2 months until the admission test 😭
and other parts in the exam too
I remembered there's also one type of systems where you have to let $y = kx$
1 divided by 0 equals Infinity
Can be applied if 2 equations share the same degree
what if they're asymetrical?
,w asymetrical
they imply a clue inside
it depend because not all problems are the same
If one of your equations are degree 1 the yk what to do right?
x^2 + 6y = 6x, y^2 + 9 = 2xy
💀
but they never seem to be sadly
Is that from your book or you made that up?
book
,w x^2 + 6y = 6x; y^2 + 9 = 2xy
there are several way you can try, for example try to subtract the two equations together
I got something that shouldn't be applied in here but somehow works
do tell
Check $x = 0$ first
1 divided by 0 equals Infinity
If $x$ ain't 0 then let $y = tx$ and substitute
1 divided by 0 equals Infinity
nah it doesn't work on second eq
you can try to add the equations together
Or you can do that and it will get you something good
(x-y)(x-y-6)+9=0
i can't get the constant in
bro not just 🙏🏼
(x-y)^2 -6(x-y) + 9
you see the x-y ?
that's similar to x^2 -6x +9
Blud ain't completing the square 😭😭😭
i forgot to do that and just factorized 😭
so we get x-y-3=0
which can fit back into first eq
Looks good
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do part b
|t-a| <= b is the same as ? <= t <= ?
yeah but i cant put my finger on what it is
write it down
|y| <= b is the same as max(y,-y) <= b (so y <= b and -y <= b)
so -b <= y <= b
wait
okay this makes sense
but in the question we have 2 different limits
do this first
we'll come back to what role 5 and 13 play afterwards
|t-a| <= b
so t-a <= b, a-t <= b
directly use this