#help-33
1 messages · Page 90 of 1
that... shouldn't matter
(i have no clue what you are talking about)
show an example pls
xD
sorry.
I have to go
Im about to loose it
I need to go for a walk lol
Sorry for that
Ty for the help from before tho
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Here only -sqrt3 is correct?
@dire ermine Has your question been resolved?
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does somebody can help me with physics ?
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✅
<@&286206848099549185>
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I’m trying to find the solutions for this but I’m a little bit confused. What’s the difference between the equation above and if it was just sin(t) and not 1/sin(t)?
Does the difference between 1/sin(t) or just sin(t) affect the solutions? Would it be 1/Y instead of just Y since it’s 1/sin(t)?
$\text{remind that: }\text{ }\left| \sin\text{}x \right|\le1$
Joanna Angel
think about what this might mean in your case
@clever mortar Has your question been resolved?
Ik that sqrt3/2 is less than one, but idk where to from there
Or what to do with that info
Ik that if it was sin(t)= sqrt3/2, I would have to look for a point on the unit circle that has a y value of sqrt3/2, but does this change if it was 1/sin(t)?
but you must also thikn how sint = , in your equation
it is not sqr(3) / 2
$\frac{1}{\sin\text{}t}=\pm\frac{\sqrt{3}}{2}\Leftrightarrow \sin\text{}t=\pm\frac{2}{\sqrt{3}}$
Joanna Angel
analys e it now
what is your conclusion then?
ok
I accidentally wrote 1/sin for step 5
Otherwise it would have been correct as just sin(t)
Right?
can you change it in yoru paper and pase it corrwect ?
now i agree
🙂
$\sin\text{}t=\frac{\sqrt{3}}{2}\text{ }\text{ }\vee \text{ }sin\text{}t=-\frac{\sqrt{3}}{2}$
Joanna Angel
haha ty
Is this correct
yes and you can add 2kPi to every such soution
Ok tysm
yw)
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can someone explain how to do 2a.
how do I find the distinct words?
I used 10! to get all possible arrangements but they arent distinct as repeating As and Ns
@steady mural Has your question been resolved?
you divide by the factorial of appearing letters
so BANANARAMA has 5 As and 2 Ns
in practice, this would look like: 10! / (5! * 2!)
It has different properties
Wow they basically gave it lol
Its 10! / (5! * 2!)
The solution is to find the distinct letters
And count how many there are
FOr example in the word "two"
They are all distinct letters
So its
3! /(1!*1!*1!)
WHich is just 3! Lol
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I need help
ask away
Don't ask to ask
Oke
thanks guys
So you don't need help anymor?
np
nope
@lilac fulcrum Has your question been resolved?
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.rotate
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The length of segment AB is 12 centimeters. Point M is taken on this segment. Find the lengths of segments AM and BM if 3AM=2BM
<@&286206848099549185>
take a ratio
AM/BM = ?
3/2?
yea
Oh yeha my bad
mhm
mhm
so now we can express AM as 2k and BM as 3k where k is a positive integer
? - ?
AB = AM+BM = 2k+3k = 5k
5k = 12, k = 12/5
substitute k=12/5 into AM = 2k and BM = 3k
Answers say that its 7 and 5
huh
wait
Idk
WAIT
yes?
Sorry 3AM doesn't equal to 2BM
.....ok
3AM - 2BM=11
what is it
Damn my bad
Oof
2y not 3y
Question mark
Question mark
Yeah correct
and because $$x+y=12$$
Question mark
$y=12-7=5$
Question mark
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
$$y = 12 - x $$ substituting into 3x - 2y = 11 $$x=7$$
David K.
Thanks guys
$$y = 12 - x $$ substituting into $3x - 2y = 11$ $$x=7$$
Question mark
looks better~
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wouldnt both probabilities be higher than 1?
probability can't be higher than 1
show me your calculations
i said P(B|A) = P(B intersect A) / P(A), as A is a subset of B then P(B intersect A) = P(B), so P(B|A) = P(B) / P(A)
as A is a subset of B then P(A) <= P(B)
then P(B|A) => 1 ?
no no
$A \subset B \implies A\cap B = A$
artemetra
not B
ohh wait true lol
you are confusing it with $\cup$
artemetra
wait but if B happens shouldnt A also happen tho
yes
there are some possible outcomes in B that are not in A
but all outcomes in A are also in B
ohhh and if A happens since it is inside B then B must happen if A happens
yes
ok so similarly P(omega | B) = P(omega intersect B) / P(B), as P(omega intersect B) = P(B) then P(omega | B) = 1 ?
yep
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A function $f:\mathbb{R}\to\mathbb{R}$ is additive and satisfies $f(x)f(\frac1{x})=1$. I need to find all functions f
kheerii
I choose $y=x+\frac1{x}\implies f(y)=f(x+\frac1{x})=f(x)+f(\frac1{x})=f(x)+\frac1{f(x)}$
kheerii
so, $|y|\ge 2\implies |f(y)|\ge 2$
kheerii
is this a boundedness condition?
if I recall, the last inequality has to be reversed for boundedness to occur
like, |f(y)|<=M for some M in some range of y
@lucid zenith Has your question been resolved?
<@&286206848099549185>
take $n \in \mathbb{N}^*$, then $f(n) \cdot f \left( \frac{1}{n} \right) = 1 \iff f \left( n^2 \cdot \frac{1}{n} \right) \cdot f \left( \frac{1}{n} \right) =1 \iff n^2 \cdot \left( f \left( \frac{1}{n} \right) \right)^2 = 1$
LF
what is N*?
non zero positive integers
ah ok
and you can solve for f(n)
so we get $f(\frac1{n})=\pm\frac1{n}$
kheerii
but that won't give us any info about irrationals
I am trying to prove that f is bounded on some interval so I can use $f(x)=cx\forall x\in\mathbb{R}$
kheerii
which would give us the result directly
we suppose that f is continuous?
no, if f were continuous then the result would follow directly
Cauchy's functional equation is the functional equation:
A function
f
{\displaystyle f}
that solves this equation is called an additive function. Over the rational numbers, it can be shown using elementary algebra that there is a single family of solutions, namely
f
:
...
I need to prove one of these three conditions
right
actually i think you can show its continuous
it might be easier than using boundedness
especially since you only need continuity at one point
at what point?
LF
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Is there any way to do this in one step in Wolfram Mathematica?
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Let R be the set of all realnumbers and 𝑹𝟐 = {(𝒙𝟏, 𝒙𝟐): 𝒙𝟏, 𝒙𝟐 ∈ 𝑹}, then which one of the following is a subspace of 𝑹𝟐 over R?
a){(𝑥1, 𝑥2): 𝑥1 > 0, 𝑥2 > 0}
b){(𝑥1, 𝑥2): 𝑥1 < 0, 𝑥2 < 0}
c){(𝑥1, 𝑥2): 𝑥1 ∈ 𝑅, 𝑥2 > 0}
d){(𝑥1, 0): 𝑥1 ∈ 𝑅}
do you know what properties a subspace must have?
could you be more specific?
i think you know what a subspace is, but i just want to be sure lol
Ahh yes. I understand the properties but I don't know how they applied
so a subspace is closed under addition and scalar multiplication, and also contains the zero vector
Yes yes
so for each of your candidate subspaces
B is discarded
you must verify these properties
you're right, but why?
1st and 2nd doesn't have addition idenity vectors
why does that matter?
If i multiply B with any negative numner
i.e. for any (x1,x2) in B, is c(x1,x2) in B?
It will give positive vector
thats right
and such a positive vector cant be in B
Same thing go to 1st option
yup
same thing
They have real and 0 both vectors
let's start with C
Yes
why do you think so?
if i multiply x2 with a negative number
(-2x1,-2x2)
But here x2>0 should be
Which is failed right?
yes
I see i see
It will ne negative
then cx2 is negative, yes
well D is closed under addition and scalar multiplication, yes
so it is a subspace of R^2
I see i see now i understand how things work and oroperties
(x1,0) + (y1,0) = (x1+y1, 0) and c(x1,0) = (cx1,0) and (0,0) is in D
Most of question can be checked with scaler multiplication
don't forget addition though
sometimes a subset is closed under scalar multiplication but not addition
Addition identity is must?
but yes, scalar multiplication is usally faster
the additive identity need not be part of the subset in order for it to be a subspace
but the subset should be closed under addition
so if the subset is called W, then for all x,y in W, x + y should be in W
yes
I have read definitions but you know things can be clear when we see in examples
indeed
👍
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Each of them I got 0, it's impossible? 4b) ODE question
@echo jolt Has your question been resolved?
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If a/b=11/13
What will be value (a^3-b^3)/(a^3+b^3)
I solved it by expansion of cube a+b and got 0.25
I would just write a = (11/13)*b
Replace every instance of a with this expression
And it becomes $\frac{\frac{11^3}{13^3}-1}{\frac{11^3}{13^3}+1}$
rafilou2003
rafilou2003
Then you will get a negative result
It just boils down to calculations, so might be simplified with some cubic formulas
11³ will be pretty easy
11² is 121
And then 121×11 = 1210 + 121 = ...
1331
Then for 13³ you get 169×13 = 1690 + 507 = ...
2197
And then hard division
So no real need for computing the decimals, but maybe just checking for common factors to simplify
@halcyon cradle Has your question been resolved?
Not very long, only 2 is a common factor
-866/3528 = -433/1764
And here's the (atrocious but in simplest form) answer
I'm just gonna put this comedic gem here
And a/b = 11/13
First of all if both a and b are positive, you can easily see that a < b and so a³ - b³ < 0 so the result is negative
Very wanky question
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I can only see the sequence is like
tan9° tan27° tan 45°tan63°
Discord is having media issues. Please transcribe your issue in text so we can see your problem.
tan(π/20) ×tan(3π/20) ×tan (5π/20)× tan(7π/20)× tan(9π/20) is equal to
A 1
B -1
C 1/2
D none
big sad
U need brackets 😭
on the last two as well
🙄🙄
@halcyon cradle Has your question been resolved?
I see thanks samuel
Let me try
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How do I get from top to bottom? Do I use partial fractions? And K is the constant
Multiply top and bottom by K of the left hand side
You can always multiply the numerator and denominator of a fraction by a nonzero number
Oh okay
Then the rest I just use the partial fractions to finish off with ln
Thanks
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hi i'm doing the junior maths challenge (first time in intermediate bracket), any tips? thx
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if you can have any amount of positive integers that sum to 2023, how can you pick them such that their product is maximised?
i think it might be something to do with am-gm but i'm not sure
usually when you see some nonsense like this if it's not immediately obvious you probably want to try with smaller numbers first
and see if you can gain some intuition
what sort of things would you need to do to solve this question specifically though
instead of 2023 try smaller numbers
like numbers you can quickly maximize
although there is one idea that if you come up with lets you solve the question in about 3 minutes
hmm so to get the biggest product you have to spread the numbers out as evenly as possible (not sure how to word it)
say the number that it summed to was 10
if you had 2 positive integers you would use 5,5 (can just do 10/2): product = 25
if you had 3 positive integers you would use 3,3,4 (10/3 is a decimal, 3.333, so you would have to use 4s and 3s): product = 36
if you had 4 positive integers you would use 2,2,3,3 (10/4=2.5, using 2s and 3s): product = 36
if you had 5 positive integers you would use 2,2,2,2,2 (10/5=2): product = 32
so the observations are that the product peaked at a point, then started decreasing again
how would you find the point at which the product peaks for an arbitrary number (like 2023 in the original question)
think about the following thing:
what's the biggest number you would ever want to pick for any arbitrarily large number
to get you started, you would never want to pick 1000, because 500 + 500 = 1000 contributes the same amount to the sum but contributes 500*500 = 25000 instead of 1000 in the product
well, you would want the number of integers to be obviously less than the sum (that would give you a product of 1)
and if you number of integers is just 1 then the product would just be same as the sum
not sure how to find the maximum though
you should probably keep trying to lower that biggest number
you can actually make it pretty low
not sure what you mean by that
what's the biggest number you would ever want to pick, in your bunch of numbers, to sum to some target (in this case 2023), while trying to maximise your product
it's smaller than 1000 (because if you ever pick 1000 you should pick 500+500 instead to get a bigger product)
if you keep going by that logic you can make that biggest reasonable number very very low
no by your own example
meaning you would have to put a 1
you already showed in your own example that when you want to sum to 10,
2 * 2 * 2 * 2 * 2 is smaller than 2 * 2 * 3 * 3
uh, i guess?
so what does that have to do with this
it lets you narrow down very quickly how you should choose numbers once you get the right largest reasonable number
have you tried lowering the bound i gave for you yet
i already gave you a starting point of 1000
umm
i guess you can keep going down until 125
after which it becomes a decimal
you don't have to always divide it by 2..
so it has to be made from 2s and 3s?
yes
if you don't need to show a proof you're basically 99% done, if you need to show a proof you're maybe say 85%
right so im guessing we need to use as much 3s as possible
2022 is a multiple of 3 but that gives only 1 left
2019 is also a multiple of 3, leaving 4
2019/3 = 674
so the maximum would be 674 3s and 2 2s?
yup
you might do the whole lowering largest number and keep going, or through some other method
and eventually you would find that the largest reasonable number is 4 (which is equal to 2 * 2 but doesn't matter)
and then you would want to show that if you pick any number larger x>4 you have a way to pick 2 numbers a, b such that a+b = x and a * b > x
which rigorously shows that the largest number you would pick is 4
then you have to show that picking a bunch of 3s first is better than picking a bunch of 4s
is there any way to do it algebraically
for which part? if you mean picking a,b
pick a = 2, b = x-2
then try showing the result yourself
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$\int^1_{-1} \frac{\ln{(x+1)}}{x}dx = \frac{\pi^2}2$
ykj3
I need to prove this but don't know where to start made the subs x <- 1/x
also did x <- x - 1 and tried ibp
Did u try substituting u = ln(1+x)
doesnt do anything
Differentiate it too, to replace dx
With du
du=dx/1+x
dx=du(1+x)
Where x = e^u-1
So dx = (e^u)du
This doesn’t have an elemental solution I think
yeah i did that the integral becomes ue^u/(e^u - 1)
for those bounds it does
ok nvm
looks like i just use dilogarithm inversion formula
1/2log(-x) term vanishes at x = -1
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Is this correct? The black line that I drew
And Is this formula somehow tied to Pythagorean theorem?
Yes
It's essentially pythagorean theorem applied twice
Wdym by twice?
Think of it like finding the length of the diagonal of a rectangular prism
If you apply Pythagorean theorem on one of the faces, you get the diagonal of the face
If you apply it again on that face diagonal and the 3rd dimension, you get the space diagonal
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having trouble with b
I found g(f(x))
but I'm not getting the answer
this is what I got
$(\frac{-2x^2+24x+2}{x^2-1})(-2)$
mj
how did you get this?
subbing and simplifying
my concern isn't with this
it's correct
it's b
got it
I assume it's multiplied by -2
hmm
that would've been
much simpler
let me try that though
yrp
yep*
getting it now
thanks
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Hi, could I get some help with this weird task?
“Mathematicians are strange sometimes,” thought the inspector.
“We had all of these partially filled glasses lined up on a table one after the other.
Only one of them had poison in it, and we wanted to know which one before we drank the glass
Examined fingerprints.
Our laboratory could have examined the contents of each jar, but these examinations cost money
Time and money, so we wanted to examine as few as possible. We called in the
University and they sent a mathematics professor to help us.
He counted the glasses, smiled and said:
'Take any glass you want, Commissioner, and we'll do that first
investigate.'
'But wouldn't that spoil the whole investigation?' asked the inspector.
'No,' he said, 'this is the beginning of the best selection process. We have to do a glass first
investigate. It doesn't matter which one it is.'«
“How many glasses were there at the beginning?” asked the inspector’s employee.
»I can't remember it exactly. Any odd number between one hundred and
two hundred.”
Determine the number of glasses.
Explain that the math professor's method was not the best.
I dont even know how to start
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wouldn't the domain of $log_3((2x-1)(x+4))$ be $x>0.5 or x>-4$?
!
show work
the orignal question
the answers
what I did was I factored the inside of the log
by doing product/sum with -8 and 7
$log_3(2x^2+8x-x-4)$
!
$log_3(2x(x+4)-1(x+4))$
!
oh ok so you need $(2x-1)(x+4) > 0$ right?
hayley
no
or i mean number line thing
okay so
doing that
I get a positive sign
from -4 to -inf
and 1/2 to inf
so therefore x>1/2 or x<-4
ah i see now
ye
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i need help
with this
what do you not understand?
Where is 2r
i mean 2x
oh i mean x^2
oh
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Any hints on this cant think of a way to do this
disregard the "largest possible" portion for now
what is the domain of that function?
The domain is the inputs a function can take
what values of x can this take as an input
$\mathbb{R}$
luke1
correct.
oh,ok
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whats the approach for this question
would you agree that this problem tells you that he walks such that the required distance is minimized?
yes
alright
for problems like this, you want to reflect one of the points over the line which he's required to touch
in this case, you could reflect point Q over the x-axis
and the straight-line distance between P and Q is the minimum
ohh image concept
ok I'll give it a try
thank you for helping
i got the answer
nice 🎉
thank you
welcome 
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o so i got a pyramid with a triangle as a base the lateral edges are sqrt70 sqrt99 and sqrt126 the latral edges are also perpendicular to each other i need the vlume of the pyramid and the area of the base
i alr found the sides of the base and the area too i need to find the hight of the pyramid now
<@&286206848099549185>
<@&286206848099549185>
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can someone tell what to do next to get angle gpb
like what to do to get the measur of pb
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im not sure why the angle is wrong
i thought the angle should be (pi/2) - arctan(20/5)
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ok so i got a pyramid with a triangle as a base the lateral edges are sqrt70 sqrt99 and sqrt126 the lateral edges are also perpendicular to each other i need the vlume of the pyramid and the area of the base
i alr found the sides of the base and the area too i need to find the hight of the pyramid now
i alr know the area of the base
now i need hight of the pyramid so i can find the volume
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i thought the angle should be (pi/2) - arctan(20/5)
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How exact does the answer need to be? (pi/2)-arctan(20/5) = 0.244978...
Also worth noting child is moving east of North, and if North is 0 radians, then typically directions clockwise to the 0 direction are considered negative
@tardy idol
it was the exactness thanks 😭
thank you for this too
.cloae
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Is this correct?
off topic, but you're icelandic?
isn't -4a+5a=a
Yes
don’t forget to add brackets after expanding the (a+5)(a-4)
the answer sholud be|| 2a^2 - a + 20 = 0|| assuming you are just simplifying?
cool i am too
I see
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Having trouble understanding thjs Consider the pictures below. Each angle
θ
is an integer when measured in radians. Give the radian measure of the angle
Pheta = 150
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Need help
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hi
can anyone helps
That is hard to read
Using SOHCAHTOA you know Tan(x) = Opposite/adjacent
cos(x) = adjacent/hypotenuse
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no its not
Yes it is the top is
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anyway to represent a semi circle explicifity
like f(x) = ..
instead of (cos(t), sin(t))
f(x)=sqrt(1-x^2)
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Hello, I've been working on the question shown in the image and got to the conclusion that after 20000 years of death, there is around 8.89...% or 8.90% of carbon-14 remaining, could anyone double check this? There aren't any answer sheets.
I'm really not sure of the method I've used to solve this, so I'm not sure if I got it correct at all
well show us your method
alright
you can ignore the finding r part
<@&286206848099549185>
Please ping me if you decide to respond, thx
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4 + 24 + 144 + 864 + ...
this is geometric right?? so you can find the ratio with the formula below
i did the formula below with 24 (2nd term) = (4 (first term) * (r^2 -1)) / r-1 (i did r^2 cuz snd term)
what did i do wrong??
!xy
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
first one
...
24/4 isn't 5 and 144/24 isn't 5 and 864/144 isn't 5
ok yeah ik but you should be able to get r from the formula right?
you can also take off your left shoe by sticking your right hand between your legs from the back, and doing a one-handed handstand on your left while doing it
just because you can doesn't mean you should!
(and you messed it up in some way anyway. no, don't ask me to fix it. refer back to the handstand analogy.)
alr thx, so just do it simplier
thx
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How do you find the solution to the inequality
@lofty wren what have you tried so far
Trying to see what numbers are on the inequalitys if thats what its called like the numbers on top
But im lost
Can u tell me like the steps without telling me what to do
with the numbers
so you can do this in proper way or redundent way
you can try each point on both inequalities and see who fits both
or you can build a graph, draw both inequalities and see where each point stands
makes sense @lofty wren ?
what you are trying to do here is see if which x,y combination from the alternatives satisfies both inequalities at the same time
from what i said, what is confusing ?
Okay so
I think i understand
so with each point i put the numbers in them and see which equations are true like but both of them have to be true
yes
so i put 0 next to 1/2?
and then 5 at y
exactly
okay
this is the redundent way tho
Im gonna try
it gives you the solution but it's not very effective if you have a lot of points
that's why the next step is to draw both graphs
Oh
and from there you have a visual representation of all points that belong and don't
to the shaded area?
yes
that sounds easier
Alr hold on im gonna pull one up and do that
how do i find out the shaded part
this would be -1/2x+5
m is negative so slope is downhill
and c = 5 so y is 5 for x = 0
ok
we like y so that y is equal or lower than the graph
so the line itself is a solution
okay
cause we like all y that are equal to y in the graph
and everything that sits lower than the graph
yes
this is all the points that satisfy the first inequality
lets start with the second one now
okay
now the inequality says, y has to be equal or bigger
so whatever is in the line and bigger value than the line
okay
Can u put them together now
alright
wherever we see colors colliding
we know that sector is a solution to both inequalities at the same time
So those would be right?
exactly
Alright
each point you have on alternative you check on the graph
on alternative?
sure 1 sec
A also is a solution
so A E and B are the solutions to both inequalities
:)) if you have any confusion lmk
Thank u
what do u use for this btw?
geogebra
you can use it but i would advise for your own benefit to try and draw them yourself to become faster at solving function and graphing them
yea i just looked at it and it looks confusing
I tried the first one i think i did it right but how do i graph a fraction?
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can someone explain how the inclusion exclusion plays into here
for each prime p that divides 210, there are 210/p numbers that are not coprime with 210
but also for each pair of primes p1, p2 that divide 210, we've overcounted the 210/(p1*p2) numbers that share a factor of both p1 and p2
and similar for all triples of primes, etc.
so you're summing up 210/p for prime p dividing 210, minus the sum of 210/(p1 * p2) for p1 < p2 dividing 210, plus the sum of 210/(p1 * p2 * p3) for p1 < p2 < p3 dividing 210, minus ... (by inclusion-exclusion)
so youre saying it would be phi(210) = |[210] \ {X2 U X3 U X5 U X7}|
which is just [210] - |X2 U X3 U X5 U X7|
but then isnt |X2 U X3 U X5 U X7| = |X2| + |X3| + |X5| + |X7| - |X2 U X3| - |X2 U X5| - |X2 U 7| - |X3 U X5| - |X3 U X7| - ...
\begin{align*}
\varphi(210)&=n-\left(\sum_{p\in{2,3,5,7}}\frac{n}{p} - \sum_{p_1<p_2\in{2,3,5,7}}\frac{n}{p_1p_2} + \sum_{p_1<p_2<p_3\in{2,3,5,7}}\frac{n}{p_1p_2p_3} - \sum_{p_1<p_2<p_3<p_4\in{2,3,5,7}}\frac{n}{p_1p_2p_3p_4}\right)\
&=n\left(1-\sum_{p\in{2,3,5,7}}\frac{1}{p} - \sum_{p_1<p_2\in{2,3,5,7}}\frac{1}{p_1p_2} + \sum_{p_1<p_2<p_3\in{2,3,5,7}}\frac{1}{p_1p_2p_3} - \sum_{p_1<p_2<p_3<p_4\in{2,3,5,7}}\frac{1}{p_1p_2p_3p_4}\right)\
\end{align*}
Desync
you could just compute it at this point, but you can simplify it using the product form of the totient function
they did it like this which confuses me
do you know what the X subscripts notate?
I think its multiples of
oh
well, that's the same thing as this really
the |X2| + |X3| + |X5| + |X7| is the first sum I gave
the next minus ones are all the pairs
etc.
oh so like because 2 times 3 and then 2 times 5 and then 2 times 7
for the sets that have a multiple of a prime
yeah
why are you adding 30, 42...
inclusion exclusion
when we subtracted the pairs
we accidentally subtracted all the triples as well
so we need to add them back in
but now we've double counted the factor of all 4, so we subtract that back off
oh like 2 x 3 times 5
yes
is there a good video youd recommend for this general concept, i think my understanding is kinda weak
Like i think the problem is i memorized the general formula but then couldnt apply my understanding
another one is: how many ways are there to partition [n]={1,2,3,...,n} into exactly k non-empty subsets? (much trickier than the previous 2)
have a go at these problems
you can do them with inclusion-exclusion as well
this is sorta like counting stuff right
thanks, also off topic but can you use P(N) to show something is uncountable since there exists no bijection between P(N) and anything
no bijection between P(N) and anything countable yes (by cantor's theorem)
