#help-0

1 messages · Page 697 of 1

arctic wren
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@flat tundra i think it's 1/2, because you have 2 possibilities or is head ou is tails

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But i'm not sure, i'm really bad at probabilities

flat tundra
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Basically you have 2 coins , one is head head (hh) , and one is head tails (ht). If one coin is picked ,and one of the sides showed it's a H , this is one of 3 possible scenarios , because the scenario in which the side showed is tails is eliminated

flat tundra
arctic wren
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The other dide must be head or tail

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So it,s 1/2

arctic wren
flat tundra
# arctic wren The other dide must be head or tail

If the side is not showns there are 4 scenarios:
Pick coin HH , flip and get h .
Same scenario as above but with the other side.
Pick coin HT and the side up is H so it gives T , or the other way around , so it gives H

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But since we know that the shown side is Head the possibility in which tails was the side facing up is not there anymore

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And from this we get to 2/3 probability of getting head again

flat tundra
alpine sable
#

Here's what I'm thinking, if you care for my input (I am also a bit terrible at probability):
So, we grab one coin. We know there are only two coins, HH and HT.
We pick one coin with the coin on H. We know there is one more coin in the box, but the one you're holding is either HH or HT. We won't know unless it's flipped.
When flipped, it can either be heads or tails, since there are two coins with different outcomes on one side, and I conclude it's 1/2. (Take this response with a grain of salt)

What would the scenario be with three coins, two of which are HH, one HT?

flat tundra
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This changes things

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Because you change the parameters

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On of all the 4 possibile scenarios , the one in which tail is facing up , is not possible anymore

velvet pelican
#

Hint: ||use the conditional probability formula||

flat tundra
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So there are not 4 scenarios

civic rivet
#

Can anyone come Discord and help us by our problem? We think it is simple but too hard for us to solve xd

arctic wren
velvet pelican
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@civic rivet please post in an unoccupied channel

flat tundra
alpine sable
#

The way your explanation sounds with the three different scenarios is making it sound like you pick the HH coin twice as much than the HT coin.

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We need a probability expert here lol

velvet pelican
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Basically $P(\text{HH coin | we see H}) = \frac{P(\text{HH coin AND we see H})}{P(\text{we see H})}$

arctic wren
#

@velvet pelican that's it?

velvet pelican
#

yes

arctic wren
#

So, it must be 1/2 cause the numbers of intersection between A and B is 1 and the number of A is 2?

flat tundra
# alpine sable The way your explanation sounds with the three different scenarios is making it ...

The possibile scenarios are: taking the hh coin on one side , and that side is h , doing it again with the other side and it's H again , taking the ht coin and doing the same process we get one scenario with a h outcome and one with t outcome. But now were given an other parameter in the question, it says that the side shown is H , and this is 100% true, if the shown side is H the scenario in which the shown side is T is impossible, so it's out of the data of the problem,

velvet pelican
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$P(\text{HH coin }| \text{ we see H}}) = \frac{P(\text{HH coin AND we see H})}{P(\text{we see H})}$

ocean sealBOT
#

Frosty
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

velvet pelican
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ok this works

flat tundra
velvet pelican
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what's your final answer?

flat tundra
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66.66666...%

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Of getting H

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2/3

velvet pelican
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the question asks for the probability that you have the HH coin given that you flipped a H

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so I believe that is incorrect

arctic wren
# velvet pelican no, it's not

So the numbers of intersection between coin 1 and coin 2 is 2, because we have 2 H left, and at total we have 3 Heads, is that correct?

velvet pelican
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you can't intersect the number of H

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that is the intersection of probabilities

woeful pulsar
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there are two hh coins and one ht coin?

arctic wren
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No

velvet pelican
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no 1 of each

woeful pulsar
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yeah then what's wrong with 2/3

velvet pelican
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wait actually nvm

flat tundra
velvet pelican
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it's (1/2)/(1/2 + 1/4) = 2/3

arctic wren
#

I still didn't get why is 2/3 and not 1/2

flat tundra
woeful pulsar
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because if you have no evidence it would be 1/2, the conditional probability changes based on the evidence

flat tundra
velvet pelican
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yes

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sorry

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I put in the wrong numbers

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earlier

velvet pelican
flat tundra
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No , I'm the one who's sorry haha , I know very little about math , so I had to verify if my process was right

flat tundra
velvet pelican
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Monty hall problem, it was a gameshow some decades ago I think

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you had 3 doors, 1 with a car and 2 with goats

flat tundra
velvet pelican
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you pick one of the doors

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then the host (who knows what's behind which door) opens a different door with a goat

alpine sable
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oh HI

flat tundra
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Ok , yes it has the same logic

alpine sable
#

is anybdoy free right now

velvet pelican
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now you get the choice to switch or keep your door

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and the question asks whether you should switch or not

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to maximise the chances to get the car

flat tundra
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Ok wait

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Let me think

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We say that the car is 1

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And the goats are 0

candid torrent
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@alpine sable i can help you

flat tundra
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001

candid torrent
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but this channel is occupied

alpine sable
flat tundra
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If you choose 0 it shows you the other 0 , if you switch you get 1 , of you choose one , he shows one of the 0s you switch and get the other 0

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So if you accept to switch choosing the car would lead to goat and choosing the goat would lead to car

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So yes ? @velvet pelican

velvet pelican
#

yes

arctic wren
velvet pelican
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||no, the answer is you have to switch||

flat tundra
# velvet pelican yes

The coin one was easier, it think this one would have taken me a lot longer without knowing it worked similarly

arctic wren
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Why??? I still didn't get this and the coin

flat tundra
velvet pelican
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it's similar in the way that knowing that when the host shows a goat in the other door, the probabilities change

arctic wren
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Yes

velvet pelican
#

btw if you switch the door, you have a 2/3 chance of getting the car

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and 1/3 chance of getting the goat

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so it's much better switching

arctic wren
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I'll try to understand

flat tundra
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Sorry if it is a bit messy

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I may have made some errors too , I'm tired and not a native speaker

arctic wren
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Thankks

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But the goat and car , no

flat tundra
# arctic wren But the goat and car , no

It has the same process , try to make a diagram , keep in mind that the variable that changes is that you are shown one of the doors with a goat that is not the door you choosed

ocean sealBOT
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TheMane3

warped phoenix
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If I vertically stretch the above function by a factor of 2 and then reflect it across the x-axis, the function would become

ocean sealBOT
#

TheMane3

warped phoenix
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right?

fluid kite
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63>77

warped phoenix
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?

flat tundra
warped phoenix
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hmm...the answer was $f\left(x\right)=-2\sqrt[3]{x+3}+14$

ocean sealBOT
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TheMane3

warped phoenix
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and i have absolutely no clue where the -14 came from

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anyone know??????????? D:

flat tundra
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You had to multiply it by 2

warped phoenix
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ah, what's the concept/reasoning behind that, if any? Or is it just a rule for transformations

flat tundra
fluid kite
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16>33

warped phoenix
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u good? @fluid kite

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yeah makes sense

fluid kite
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it's a riddle

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if anyone gets it dm me

warped phoenix
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...

fluid kite
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44>33

flat tundra
warped phoenix
fluid kite
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which?

warped phoenix
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@fluid kite well if you need help solving the riddle, than any of the question channels, if not, then go to #chill or #math-discussion

fluid kite
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k

warped phoenix
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and yeah shanti makes sense because if I put $f\left(x\right)=-2\sqrt[3]{x+3}-7$ into desmos then its not reflected across the x axis

ocean sealBOT
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TheMane3

arctic wren
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How can i demonstrates that ? $lim [sin(\theta)/\theta]; \theta \to 0$ I've seen the demonstration but didn't get it

ocean sealBOT
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Guilhotina

sage jacinth
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also

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that goes to 1

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not 0

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if you want it to go to 0 you have to take the limit as $\theta$ approaches infinity

ocean sealBOT
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(バカ) baka

alpine sable
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someone help me with this

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Pls

rich basin
lethal stump
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perms and combs is probably my weakest subject but it should be 1/2 right?

rich basin
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Yeah, but i was wondering why is my answer wrong

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this is what I have right now $\frac{3C1\cdot 5C1 + 3C1\cdot 5P2+ 3C1\cdot 5P3 + 3C1\cdot 5P3 + 3C1\cdot 5P4 + 3C1\cdot 5P5}{
6P2 + 6P3 + 6P4 + 6P5 + 6P6}$

ocean sealBOT
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BorutoEyePower

rich basin
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$\frac{3C1\cdot 5C1 + 3C1\cdot 5P2+ 3C1\cdot 5P3 + 3C1\cdot 5P3 + 3C1\cdot 5P4 + 3C1\cdot 5P5}{
6P2 + 6P3 + 6P4 + 6P5 + 6P6}$

ocean sealBOT
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BorutoEyePower

rich basin
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I could explain how i managed to get this location if you want?

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<@&286206848099549185>

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I understand that it is 1/2 based on that either one having 50 percent of being chosen even or odd

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Butt i just want clarification on why this won't work

arctic wren
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is there a chat to talk about another thigs besides math ?

lilac lantern
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Why is the integral of 1/u = ln|u| and not ln(u) , like why is it || ? does this mean it is the ln of the absolute value of u?

rich basin
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@lilac lantern I thought this wasn't an integral question?

lilac lantern
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Yes its just a general question lmao

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Ok I found the answer for myself

rich basin
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Please can anyone help me?

nocturne mirage
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whats the question sir ?

lethal stump
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the main reason for the absolute value sign is that x has to be > 0 if you want real values for ln(x)

rich basin
lethal stump
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omg

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forget what i said

rich basin
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this is what i have right now

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$\frac{3C1\cdot 5C1 + 3C1\cdot 5P2+ 3C1\cdot 5P3 + 3C1\cdot 5P3 + 3C1\cdot 5P4 + 3C1\cdot 5P5}{
6P2 + 6P3 + 6P4 + 6P5 + 6P6}$

ocean sealBOT
#

BorutoEyePower

lethal stump
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do you have answers?

rich basin
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Yeah

lethal stump
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it isn't 1/2?

nocturne mirage
#

I would say 1/2 since only the last digit matters

rich basin
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It is 1/2

lethal stump
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oh ok

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thank god

rich basin
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But i'm confused how come my working out does not give out 1/2

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Like i've taken all taken all the cases when it is even, and numbers are even when their first digits are divisible by 2

nocturne mirage
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last digit*

rich basin
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Yeah last digit

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So basically in my numerator, I take cases of various amount digits i want to make

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Like forexample $3C1\cdot 5C1$

ocean sealBOT
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BorutoEyePower

rich basin
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I choose 1 one of the 3 even numbers and then times it with the rest of the numbers left

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It doesn't matter which is picked, as long as the last digit is even. It will still work

rich basin
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I finally figured why i got it wrong

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@crisp iron

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right now i have $\frac{3^{13} \cdot 48^2}{52^5}$

ocean sealBOT
#

BorutoEyePower

hazy dome
# rich basin

I’m pretty sure you’re supposed to find each part separately

rich basin
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Isn't this with replacements

hazy dome
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It doesn’t specify

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Which leads me to believe that each part is an independent event from the previous part

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Asking as if nothing had happened before the draw for each part

rich basin
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I am confused

hazy dome
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Don’t even consider the other parts when solving for any particular part

rich basin
#

I am confused with what you mean by treating what as a separate entity

hazy dome
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Just solve each problem separately

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As their own separate event

rich basin
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this is part (a) we are talking about

hazy dome
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This is all parts

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Pretend that you’re given a full deck in part a, you draw the cards and calculate the probability, then you reset the deck and put in all needed cards then you do the same procedure for part b and c

rich basin
#

How can we solve part (a) then in your view when separating each of the entity

hazy dome
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Because once you draw those 3 hearts, it won’t matter what the next 2 cards are

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You’ve already satisfied the requirements

rich basin
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But then once you draw 3 cards, there are many other options you can draw it with

hazy dome
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But that doesn’t matter

rich basin
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Like forexample 3 hearts and 2 spades is one option and 3 hearts and 2 aces are another

hazy dome
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You’re asked for 3 hearts

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That’s it

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You could draw any other 2 cards you wanted, you still got 3 hearts

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Part a simply asks for 3 hearts

rich basin
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But then there are many ways you can get the 3 hearts though

hazy dome
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But exactly 3 hearts

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So no more no less

rich basin
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That is why it should be 39^2

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I removed all the hearts

hazy dome
rich basin
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What equation do you think it will be

hazy dome
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Basically, solve as if you draw 3 hearts in the first 3 cards, and then you draw anything but a heart for the last 2

rich basin
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Based on what you have interpretated and just doing it non replacement it would be 13C3 over 52^5

hazy dome
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(13/52)(12/51)(11/50)(39/49)(38/48)

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The first 3 are hearts, and the last 2 are anything but hearts

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I’ll have exactly 3 hearts at the end

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I’m sorry I couldn’t explain it in more detail

rich basin
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@hazy dome That is the right answer, but I am still confused

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Like isn't it supposed to be with replacement

hazy dome
rich basin
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Like you can have HHHAA

hazy dome
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It’s kind of assumed that if you draw 5 successive cards that you’re not gonna replace them

rich basin
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Doesn't it say with replacement

hazy dome
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But that’s just me

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...

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I’m dumb XD

rich basin
hazy dome
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so then it’s (13/52)^3 times (39/52)^2

rich basin
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Wait but this is wrong

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And your other answer is correct

hazy dome
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Ok now I’m confused XD

rich basin
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,w solve (13/52)(12/51)(11/50)(39/49)(38/48)

ocean sealBOT
rich basin
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Wait this is still wrong

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The only difference with the answer is with the denominator being an extra 0

hazy dome
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Wut lol

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The cubed one is with replacement

rich basin
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That is the answr i had before i'm pretty sure

wary stream
#

You're replacing the cards back into the deck

rich basin
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@wary stream Well we now have a different answer

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right now we have $\frac{3^{13} \cdot 39^2}{52^5}$

ocean sealBOT
#

BorutoEyePower

rich basin
#

@hazy dome I think there is another issue i think

hazy dome
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Idk what it is then

rich basin
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I think it is because we have duplicatse

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Like we can have AABPP

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And we can have ABAPP

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which would be the same when we select 5 cards

wary stream
#

Do you know what the exact answer is?

rich basin
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,w solve (13/52)^3 times (39/52)^2

ocean sealBOT
rich basin
#

this is the answer

wary stream
#

,w 2717/33320

nocturne mirage
#

the channel is already used, @warped phoenix

wary stream
#

This channel is busy

rich basin
#

,w solve (3^13 * 39^2) divide (52^5)

ocean sealBOT
rich basin
#

,w solve (13^2 * 2^39) divide (52^5)

ocean sealBOT
rich basin
#

,w solve (13^3 * 39^2 * 2) divide (52^5)

ocean sealBOT
rich basin
#

,w solve ( (13^3 times 39^2) divide 4!) divide (52^5 divide 5!

ocean sealBOT
warped phoenix
#

Why is it 1.9% and not 2.1% when 25/12 = 2.08?

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anyone???

rigid smelt
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oh well idk about this

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<@&268886789983436800>

tall wing
#

ah

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yeah it looks like a test

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banned

woven flume
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in matrices

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uh

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I'm trying to get A inverse = (1/88) B

alpine sable
#

Hi how do i solve this?

sudden nimbus
ember lava
# sudden nimbus

expand it, then find coefficients of p^2, p and the constant term, the values of coefficients will be a, b and c, respectively.

sudden nimbus
#

so opt 4

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??

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@ember lava

ember lava
#

yes

sudden nimbus
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ok

alpine sable
ember lava
alpine sable
#

Sure

ember lava
#

so you need 500 units of calcium

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and food A gives 32 units of calcium every ounce

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so how many ounces are needed?

alpine sable
#

15.625?

ember lava
#

yes

alpine sable
#

Oh so its division

ember lava
#

but they are telling you to round it off to the nearest whole number

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so its 16

ember lava
#

find out the others in the same way

alpine sable
#

So i add them up?

ember lava
#

yes

alpine sable
#

Like (500/32) + (470/24)

ember lava
#

yes

alpine sable
#

Thanks

ember lava
#

np

alpine sable
#

@ember lava is there any discord group for chemistry too

ember lava
#

if you want, i can send the link in dm

alpine sable
#

Yes please

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@ember lava

ember lava
alpine sable
#

Does anyone know about the card game Hand and Foot?

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Because I have an idea about the game, but I need help with it.

muted owl
#

So how am I supposed to do the working for this

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I know the answer but in general how do I show steps

vale wigeon
#

with words

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perhaps a good intermediate step is to find the common difference of this AP

muted owl
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its alright I got it

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I need to put formula and then plaece values in the formula

tired hamlet
#

How would I start this one?

plain dome
#

1+1=

tired hamlet
vale wigeon
#

"i didn't read #❓how-to-get-help and i think it's funny if i post a 1st grade math question hoping for someone to give out the answer, in violation of this server's purpose"

quiet crown
#

$2005=2183\cdot(1-r)^15$

ocean sealBOT
quiet crown
#

Ok fuck latex lol

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but i think you now just need to reverse to find the rate

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Assuming in 1990 the population was 2,005

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Which i think the reverse is

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It will look like this

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@tired hamlet

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but that fifteen will be above the square root thingy

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I'm probably way off

tired hamlet
#

Is this right or is the way you did it right?

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Oh I think I need to switch the 2183 and 2005

ionic jewel
#

,w 2183 = 2005e^(15k)

ionic jewel
#

0.0056 about

heavy canopy
#

What signs should we put in between so the result is 13?

tired hamlet
#

Oh 15 instead of 0?

dark granite
# heavy canopy

there is a question being asked here already. Please refrain from asking until this question is answered. or ask elsewhere

heavy canopy
#

Oh I didn't know that im sorry!

dark granite
ionic jewel
#

is there actually any combination?

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you can't use digision, besides between the 4 and the 2 i don't think

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and that's not useful

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i don't see a way and i don't really want to try all 256

coral cosmos
alpine sable
ocean sealBOT
#

Quinnt

alpine sable
#

Which is (3 * 7)-(4 * 2)= 21-8=13

coral cosmos
#

but can we use sqrt though

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Does it come under a sign? Because I've never heard of it

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but your answer is correct, so maybe yea

left echo
#

someone help pls 🙏🏿

ionic jewel
#

i though square roots (and parenthesis although yours don't matter are illegal)

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but fair solution then, id still call it a trick question

paper oar
# left echo someone help pls 🙏🏿

this is a 3rd (odd) degree function and in odd degree functions, it rises at one side and falls to the other which means that we can eliminate options B and D. Now since the leading coefficient is negative (-4) it will rise to the left and fall to the right, and thus it will be option C.

paper oar
#

no problem, hope you understood it.

left echo
#

also

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why does it have to rise from the left and decrease from the right? how does that correlate w the coefficient

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why cant the end behaviour go both up or down

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like they’re both positive or negative infinity

paper oar
#

because it is -4x^3 which is an odd degree and if there is an odd degree then both ends will not go to the same end behavior

ionic jewel
#

don't make him memorize all the cases

paper oar
#

yeah I guess.

ionic jewel
left echo
#

ohh that makes sense ok

paper oar
left echo
paper oar
tight locust
#

if p and q are the roots of ax^2 + bx + c then what equation yields the roots 1/p and 1/q

ionic jewel
#

(x-1/p)(x-1/q)

tight locust
#

in terms of a, b, and c

ionic jewel
#

are you trying to solve abc in terms of pq or the other way around?

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if you want a,b,c in terms of pq just multiply out how i sent it

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if you want it the other way do the quadratic eqn

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oh I'm illiterate sorry

minor heath
tight locust
#

i got it lol

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ty

dry thunder
#

the sum of 15 repetative integers in 550 find the integers?

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any help?

ionic jewel
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what are repetitive integers?

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the same one 15 times?

dry thunder
#

my bad consecutive*

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i think you can keep it like x, x+1 and so on

tight locust
#

29 thru 43

tidal grotto
ionic jewel
#

that would be an annoying expression though

tidal grotto
#

Find integers of n if possible 🙂

tight locust
#

not if you're smart

ionic jewel
#

so the better way is just doing 550/15 then using the answer as your middle term and it'll probably work

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,w (1+2^n+3^n)/5 = n!

minor heath
ionic jewel
tidal grotto
#

😠

minor heath
#

,w (1+2^n+3^n)/5 = n! over the integers

ionic jewel
minor heath
#

bruh

tidal grotto
#

(╯°□°)╯︵ ┻━┻

ionic jewel
tidal grotto
#

ME

tight locust
ionic jewel
#

it's not a diophantine common form, so idk how you expected to do it

tidal grotto
#

I thought it had integers

dry thunder
tight locust
#

so you have 15x+14*(15)/2 = 550

dry thunder
#

was asking

ionic jewel
dry thunder
tight locust
#

because the first term is x+0 so it's actually the sum from 1 to n-1

ionic jewel
tidal grotto
#

ok

tight locust
#

lmao

#

did you really expect that to have an integer solution?

tidal grotto
#

cursed_flushed yes

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wait

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how did the computer calculate the non-integer value of factorials

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it showed a graph

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confusion

jagged imp
#

it certainly cant have positive integer solutions

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since the numerator of that fraction is even

ionic jewel
jagged imp
#

wait no

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lmfao im dumb

ionic jewel
#

gamma function is a continuous extension of factorials I suppose

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,w (1/2)!

ionic jewel
#

this is a fun one @tidal grotto

tidal grotto
#

for you

#

why pi

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whyy

ionic jewel
#

😆

tidal grotto
#

btw if 0! is 1

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how can 0.5! can be lower than 1

ionic jewel
#

,w plot gamma function

tidal grotto
#

oh

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so It can get lower at some point

ionic jewel
#

except it's off by 1

tidal grotto
#

what does gamma function do btw

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like

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can I calculate by hand

thorn kindle
ionic jewel
#

,w gamma function

tidal grotto
#

um

ionic jewel
#

not given on that page

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but there is one

tidal grotto
#

oh

ionic jewel
tidal grotto
#

O_

#

wow

#

that looks so

#

cool

ionic jewel
#

🤠

#

math is cool

shrewd otter
#

😎

ivory otter
#

im supposed to prove the above identities

#

but im not sure how to continue from here lol

rich basin
#

@ivory otter I can help you if you want? unless you help me?

ivory otter
#

help you with what

#

i dont understand your offer

rich basin
#

Combinatronics

ivory otter
#

xD

rich basin
#

I will help you with trig, however yuou must help me with combinatronics

ivory otter
#

lmfao i cant help

rich basin
#

Why?

#

I've been stuck on this one question all day

vapid swift
rich basin
#

Only the doctors on mathematics can help me cure this nightmare

#

This is the only question left until I'm up to the easy part of the combinatronics section, dealing with binomial expansion

#

This morning my equation that I had is

ivory otter
lethal stump
#

ah but it will

vapid swift
rich basin
#

$\frac{13^{3} \cdot 39^2}{52^5}$

lethal stump
#

you will see when you try it

ocean sealBOT
#

BorutoEyePower

lethal stump
#

also remember that cos^2x + sin^2x =1

ivory otter
#

ye

rich basin
#

@ivory otter Try subbing it in

ivory otter
#

i did

rich basin
#

@ivory otter To solve proof question in trig, you want to try to make the functions the same as the equation that you are trying prove

ivory otter
#

you dont say

rich basin
#

@ivory otter Havee you got it yet?

ivory otter
#

i mean

#

i dont like this

#

i wouldnt have thought about this

#

unless you told me

#

how the fk am i gonna solve it like this during exams

#

i cant use discord in exams

rich basin
#

@ivory otter Don't worry, I was like you before 2 years ago. It is going to get extremely easy once you practice more

ivory otter
#

i have been practicing for days..........

rich basin
#

@ivory otter Just make sure to make the functions the same as the equation that you are trying to prove as well as the degrees

#

Degrees priority first and then the functions

lethal stump
#

also sometimes it helps to look at the question backwards

#

as in starting from the answer and thinking 'how could i make this look like the thing they gave me?'

rich basin
#

@ivory otter When is your exam?

dark granite
# rich basin

This question implicitly assumes that the order of selection doesn’t matter

ivory otter
dark granite
#

So 52^5 shouldn’t be the denominator

rich basin
#

@dark granite I thought that might be the case, how can we remove the duplicates?

#

That is the only issue I have so

#

far

#

I was thinking of dividing 52^5 by 5!

dark granite
#

The denominator must be 52+5-1 choose 5

#

Because were selecting with replacement

rich basin
#

What is with minusing 1?

dark granite
#

You may have learned that as 52 multichoose 5.

#

It has to do with boxes and balls with dividers

rich basin
#

don't know what you mean by boxes and balls?

dark granite
#

So you have 52 distinguishable boxes

#

5 identical balls

#

So you only need 51 dividers to tell boxes apart

#

So 51+5 choose 5 places the dividers down and the balls fill the remaining slots

#

Also known as stars and bars

rich basin
#

What do you men by dividers?

dark granite
#

Literally just bars that divide the distribution of the 5 balls amongst the 52 boxes.

#

If all the balls are to the left of the 51 dividers, that means we picked all 5 of say aces

#

So line up the 5 identical balls in a row. Where these balls land, represents which cards you’re selecting

lethal stump
dark granite
#

Yeah it’s fun yo

rich basin
#

I am still rather confused how can just 51 bars can divide the distributin of the 5 balls amongst the 52 boxes

dark granite
#

You’ve learned selection with repetition where order matters right?

rich basin
#

Can you please give me a smaller example?

dark granite
#

Sure

rich basin
#

So I'm right now imaging like 6 boxes and there are at least 3 bars minimal to divide them

dark granite
#

From a store that sells only three varieties of coke, I wish to order exactly two cans of coke. How many ways can I order two cans of coke if I’m allowed to have cokes of the same variety?

rich basin
#

okay

dark granite
#

So I need three distinct boxes

rich basin
#

yes

dark granite
#

And 2 identical balls

#

And 3-1 dividers

rich basin
#

How would you say the bar represents?

#

Is it like 0 | 0 | 0

dark granite
#

Using this method, if I have n distinct boxes, I need n-1 dividers to distinguish between the distribution of balls into the boxes

rich basin
#

What about something like 6 boxes

#

wouldn't you need 3 bars to divide?

dark granite
upper pond
#

how do i calculate probability

dark granite
#

You’d need 5 dividers

rich basin
#

Why is that the case for 6 ?

dark granite
#

Because 6-1=5

rich basin
#

Unless they are lined up linearly

dark granite
#

Read my comment bout n boxes

rich basin
#

yeah

lethal stump
#

wait so can you write the denominator as 5*52C1?

#

soz about interrupting anything

dark granite
#

So you’d be essentially arranging a ‘word’ with bars and balls where everything to the left of the left most bar represents one box, everything in between two consecutive bars represents another box, and everything to the right of the rightmost bar represents another box

rich basin
#

okay

dark granite
#

Make sense?

rich basin
#

yes

dark granite
#

0|0| is a different ordering of the cans of coke than |0|0 for instance

rich basin
#

Not quite make sense

dark granite
#

Well the first distribution there says I bought cherry coke and Diet Coke, but not sprite. The second distribution says I bought Diet Coke and sprite but not cherry coke

rich basin
#

Okay that now makes sense

dark granite
#

Nice

#

Where the 0 is represents that I ordered that item

#

If there’s more than one 0 in a box, that means I ordered more than one item of that variety

#

Make sense?

rich basin
#

yes

dark granite
#

Dope

#

So back to your card question

#

Essentially we’re choosing 5 cans of coke from a store that sells 52 varieties and were allowed to select cans of the same kind

#

Right?

rich basin
#

yes

dark granite
#

Hence the whole (52+5-1) choose 5 denominator

#

So what’d the numerator be for part c?

rich basin
#

is the 5 for the extra replacements that is necessary to keep up with the amount of choice the user is making?

dark granite
#

Essentially yeah, but it makes more sense to think in terms of the identical balls into distinguishable boxes idea

rich basin
#

so i think it will be like (13+3 -1 ) choose 3 times (39+2 -1 ) choose 2

lethal stump
#

yo do you have sols

#

for the qs

dark granite
#

That ain’t the answer for part c man

#

If we can’t allow hearts in the selection, just throw em away in the first place. So the numerator for part c should be (52-13+5-1) choose 5

lethal stump
#

do you guys know the answer for part a?

rich basin
#

yeah

dark granite
#

Were working on it

lethal stump
#

i was thinking about maybe using binomial probability?

#

since the chance of pulling a heart is 1/4

rich basin
#

I am still rather confused how the idea of 52 + 5 is related to the identical balls idea

lethal stump
#

and there is no replacement

#

could you do something like 5C3((1/4)^3)*(1)^2 = 5/32?

dark granite
dark granite
#

Now see it?

rich basin
#

wouldnt that be 56 chose 5

plucky sun
#

how to skip count by 6 and 7

dark granite
plucky sun
#

Help

dark granite
plucky sun
#

Well answer my question first mf

rich basin
#

Still confused with how you put it like that

dark granite
#

Like what?

rich basin
#

so you getting the divider and then you adding 5 more bars

plucky sun
#

Eo

#

E

#

Eaoa

#

Hdhhd&Hebburn

dark granite
#

Those 5 more things aren’t bars, those are the balls

plucky sun
#

Rested we've eggs seen wii eh ez u yum tea to tea to gx t yum tea yum tea

#

To ez 60 tea tea td up tea to dm tea cm f4

#

🖕

rich basin
#

can you please represent it in like a diagram out of text, maybe for a smaller example?

plucky sun
#

Answer my question first mf

dark granite
dry thunder
#

idk

dark granite
dry thunder
#

i guess thats the language idiots speak!

#

yes

lethal stump
#

mfs really tryna cast a spell on me

dry thunder
#

lmfao

rich basin
#

@dark granite like something like this 0|0|0

dark granite
#

Yeah can someone get a mod here to throw that dude outta this chat

#

Okay I see it

dry thunder
#

i think your the one whoes out

#

watch your back @dark granite

dark granite
#

No I’m talking about @plucky sun

dry thunder
#

anything can happen 😉

sly mantle
#

@plucky sun knock it off

dry thunder
#

oh ye sowwy @dark granite

rich basin
#

So in the can example where you want two cans of the same type. It will be (3+2-1) choose 2 1||

dark granite
#

@dry thunder dude I literally have no prob with you. Im just talking about that other dude who flipped us off

lethal stump
#

mathematical beef

dry thunder
#

didnt see shit

#

didnt mean too :))

dark granite
#

It’s all good just get that other dude outta here

dark granite
#

(3+2-1) choose 2 is right

rich basin
#

what about the 1||

dark granite
#

Oh I thought that was a typo you made

rich basin
#

the | is the bars

dark granite
#

Okay, why is the 1 there?

#

Where are the balls?

rich basin
#

Would you be able to please represent that scenarioo in terms of | |

dark granite
#

Sure

#

0|0| is one distribution

#

Notice there is no zero to the right of the rightmost bar

rich basin
#

yes

dark granite
#

So that particular can of Coke isn’t selected in this distribution

#

Make sense?

rich basin
#

yes

dark granite
#

Kk well there you go! You should be gold now

rich basin
#

But i'm confused with how the + 2 relates to that?

dark granite
#

You’re talking about 3+2-1?

rich basin
#

yeah

dark granite
#

Okay if I give you the word aabb and ask you to arrange the letters in that word in a row, how many distinct arrangements are there?

rich basin
#

there will be 4! divide by 2! and 2!

dark granite
#

aa represents the 2 balls (cans of coke we’re selecting) and bb represents the 3-1 dividers

#

Also known as 4 choose 2

rich basin
#

why does bb represent 3-1 dividers?

dark granite
woeful pulsar
#

please just ask in one channel

rich basin
#

yeah

dark granite
#

Replace aa with 00 and bb with the two bars

#

Now does it make sense?

#

@rich basin

rich basin
#

Sorry, I am sitll confused with the bb being two bars

#

Like i get how you do 4C2 being you choose 2 aa and the rest being the bb

dark granite
#

Okay we must place bars and balls in a row

rich basin
#

Don't quite link this to the bar idea

dark granite
#

Aabb makes up four total spots

#

Of those 4 spots place the a’s (the balls) and then the b’s (the bars) go in the remaining spots

#

The distribution of balls around the bars represents the distribution of balls into boxes

#

Because the dividers help us distinguish between what balls are in what boxes

rich basin
#

How would the aa and the bb in the idea of | |

dark granite
#

Aa is two identical letters the bars are two identical symbols

#

Okay explain this whole boxes into balls business back to me the best you can and hopefully we can figure out where your confusion is

#

Or dm me if you don’t wanna do this publicly

rich basin
#

So basically the boxes have n total boxes - 1 divisors, and we know what the distribution balls are because of the divisors

dark granite
#

Should say n-1 instead of just -1 there

rich basin
#

Yeah, and forexample something liek 1 | | , there are 2 balls in that specific type

#

whereas those who are null, would not be selected

dark granite
#

What does 1 represent there?

rich basin
#

The 1 represents that there are 2 balls in that specific type forexample, blue red and green. There would be 2 blue balls

dark granite
#

Uh okay, so how would you represent that there is only one ball in that type?

rich basin
#

0 | |

#

or | 0 | or | | 0

#

3 - 1 + 1 C 1

dark granite
#

Okay, why not just put two zeros where that 1 is originally?

rich basin
#

I thought you meant before that 0 is suppose to mean 1 item

dark granite
#

Because the way you have the 1 there doesn’t allow us to choose one item of one kind and another of another kind

#

Yes

#

To two items being selected would be two zeros

#

3 items, three zeros

#

And so on

rich basin
#

so like 0 0 0 | |

#

or 0 | 0 | 0

dark granite
#

The number of balls is the number of things you’re selecting

#

The number of bars is one less than the number of distinct varieties you have to choose from

feral apex
#

Can someone dumb it down for ke

dark granite
# feral apex

A question is being answered rn. Please wait or ask elsewhere

#

Does that make sense @rich basin

rich basin
#

Yeah i get that

dark granite
#

Dope

#

Kk so the card thing follows pretty similarly from there

rich basin
#

but don't quite see the distinction of adding the amount of balls ontop of forexample 3 +2 -1 choose 2

dark granite
#

5 identical balls and 52-1 dividers

rich basin
#

That is the only confusion I have

dark granite
#

Well remember it’s (3+2-1) choose 2

#

That whole quantity In parenthesis choose 2

#

3+2-1 represents how many spots we can choose 2 from to place the 2 dividers

rich basin
#

is it written as (3+2) -1 or is it (3-1) + 2?

dark granite
#

Or the 2 balls

#

Those are the same

rich basin
#

Lile how is it seen?

dark granite
#

Addition is associative

rich basin
#

Because i see the fifrst one as +2 being that it will firstly add the 2 replacement balls and then getting the dividers

dark granite
#

$\binom{3+2-1}{2}$

ocean sealBOT
#

logician_pdx

dark granite
#

Like that

rich basin
#

and then the second being finding the dividers first

dark granite
#

Okay yeah the way you just described doesn’t quite encapsulate what’s going on here

#

Do you mind if I chat with you bout this later today? It’s 2:24am where I live and I’m doing this from my phone so I’ll be able to provide better explanation once I’m on my laptop

#

Could ya dm me the card question?

rich basin
#

Yeath that is fine, but what would the equation be before you go?

#

Would it look something likw

#

,w solve ((13+3 -1 ) choose 3 times (39+2 -1 ) choose 2) divide ( 56 choose 5)

ocean sealBOT
dark granite
#

Yeah that’s for part a

rich basin
#

But then the answer is different

dark granite
#

I’d personally right that 56 as 52+5-1

#

The answer is different from what?

rich basin
#

it is different frm the wolfrma

dark granite
#

Wym?

#

Wolfram just calculates what you give it

rich basin
#

This is apprantly the answer

dark granite
#

That first fraction that I saw you post. Did that fraction equal this one here that you say is the answer?

rich basin
#

unfortunately not

dark granite
#

Can this answer not be reduced?

rich basin
#

,w solve 2717/33320

ocean sealBOT
rich basin
#

It has a different decimal approximation

dark granite
#

Hmm any explanations that came with that answer?

rich basin
#

They didn't say anything, this is one of the even type question

dark granite
#

That answer is wrong dude

#

And frankly textbook answers are sometimes wrong

rich basin
#

Yeah, the answer could be wrong

#

The textbook has wrong answers

dark granite
#

I’d email your prof of the answer we worked out

#

Wait really?

#

Why are you using that textbook then?

rich basin
#

This is the textbook we have to use

dark granite
#

Damn but you’ve noticed it’s had wrong answers before?

rich basin
#

I got a wrong answer question before,

dark granite
#

Wdym?

#

Your answer was wrong or theirs?

rich basin
#

Like there was a question with a wrong answer in the previous chapters

dark granite
#

Oh gotcha

rich basin
#

So there is a chance this one could be wrong

dark granite
#

Yeah def email your teacher

#

Yes! Definitely

rich basin
#

Okay thanks. I will try to DM you tomorrow

dark granite
#

Okay cool sounds good

#

When you email your teacher, I’d show em exactly what we worked out and provide explanation for our answer

rich basin
#

Good night

dark granite
#

Thanks

rich basin
#

My teacher barely reply to emails

dark granite
#

Wow

#

Maybe also Throw your Question in the competition math chat and see if other people get what I’ve got

#

Just In case your prof doesn’t answer

#

This chat is open for questions now

rich basin
#

Okay I sure will, thanks

dark granite
#

You’re welcome

clever pewter
#

This question is from a book and that book usually contains pretty less solutions (solutions to selected problems) and I am stuck on this since quite a while; I will be glad if somebody helps me prove this.

#

there's also a hint on the book and the hint says: ||use the argument used in IMO 1988 #6 or in other words use vieta jumping/ infinite descent||

#

I have made some progress as well

#

let a^2+b^2+1 != 3ab or a^2+b^2+1 = kab where k != 3
and there exists (a,b) belongs to positive integers such that a^2+b^2+1=kab
then rearranging it we get x^2-(kb)x+b^2+1=0
Let (a,b) be the smallest solution possible (a+b= minimal)
wlog assume a>=b
then let ab=l
then, a^2+b^2+1=kl

#

and I don't see how I can proceed

#

I tried to prove it using contradiction

#

<@&286206848099549185>

ivory otter
#

can i do this

#

$\int 5x^6$ $dx = \frac{1}{7} * 5x^7 = \frac{5x^7}{7} = 5x^6$

ocean sealBOT
#

MEOWBRO 父

ivory otter
#

ah shit noooooooo

#

i cant lol idk why in my head i thought it was (5x^7)/(x)

thorn kindle
#

Huh?

#

Wtf are you on man

ivory otter
#

xD

#

ok so a serious question

#

shouldnt the integral of

#

$\int 5x$ = x^5

ocean sealBOT
#

MEOWBRO 父
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

coral cosmos
#

Wait, its 5x^2/2

ivory otter
#

once again i realise my mess up

#

if it was 5x^4

#

it would be x^5 right?

coral cosmos
#

Oh yes then it would be x^5

ivory otter
#

ok

coral cosmos
#

$\int 5x^4$ = x^5 + c

ivory otter
#

ye

ocean sealBOT
#

Phantom々Rakshit
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

flat flicker
#

Hi guys, I'm trying to solve a task using gauss' method but I'm struggling a bit. Could you help me please?

woeful pulsar
flat flicker
#

Ops, yes sorry😅

vale sapphire
#

A horizontal tangent line simply means that the derivative equals 0 at that point

dark granite
clever pewter
dark granite
#

Really? Okay I’m on point

clever pewter
#

yes seems like it

dark granite
#

Suppose a=b. Then what do we have?

#

Look at the given condition

clever pewter
#

Hmph well I tried it with small values like (1,1) and it worked but how will I prove it

#

I mean that's the thing right

#

I have to prove it

dark granite
#

Bro look at what I just said

wheat hare
#

how to get the alternate form of this n/(n+1) ?

clever pewter
dark granite
alpine sable
#

@dire pilot that is a

clever pewter
dark granite
#

At first yes

clever pewter
#

and do the grunt work

dark granite
#

Then we’ll cover a>b

#

Wlog

clever pewter
#

oh

#

so you mean wlog a≥b

dark granite
#

No

#

I mean exactly what I wrote

#

Cover the equality case first

clever pewter
#

okay

dark granite
#

Then do a>b

#

So if a=b, what happens?

clever pewter
#

we can change the equation and make that a^2|2a^2+1=3

dark granite
#

No

#

Still no

#

Look at the left hand side of the divides symbol

#

There we go

#

But why did you set that equal to 3?

#

We can’t do that

clever pewter
#

so are we trying to contradict the statement ab|a^2+b^2+1=3

dark granite
#

No

#

We are directly proving the equality case holds

#

Then we will use contradiction later for a>b

#

Dude change everything back to what you had with the equality case, but delete =3

clever pewter
#

ok so

#

a^2|2a^2+1

dark granite
#

Yeah

clever pewter
#

which is only possible for a=1

dark granite
#

Nice

#

How do you know that

#

Prove it

clever pewter
#

prove it? 😳

dark granite
#

You can’t just jump from that and say it only works for a=1 without showing any work

clever pewter
#

I don't really see how I can prove my claim

dark granite
#

Does a^2 divide 2a^2?

clever pewter
#

ok I get what you mean

#

so => a^2 must divide 1

dark granite
#

Right but why

clever pewter
#

which forces a=1

#

but honestly really we need that?

dark granite
#

Yeah it is a proof right?

clever pewter
dark granite
#

We have a^2 divides two things, so it must divide their positive difference

#

And that positive difference is 1

clever pewter
#

right

dark granite
#

So a^2 divides 2a^2+1-2a^2=1

#

Since a is a natural number. Only a=1 satisfies this

clever pewter
#

yes

dark granite
#

So now we’re still not done with this equality case

#

What do we have to show?

clever pewter
#

we need to show that this whole thing =3 right

dark granite
#

We need to show 3a^2=2a^2+1

#

Just plug in a=1

clever pewter
#

yes

dark granite
#

Kk that is the end of the equality case

#

Did that part make sense?

clever pewter
#

but did we really need to show that it works lol

clever pewter
dark granite
#

Yes you’ll see why later

#

Okay so is it okay to assume a>b now? Explain why/why not

clever pewter
#

it is because even if we change the places of a and b it'll be the same

dark granite
#

Perfect

clever pewter
#

basically we don't lose generality

dark granite
#

So let’s assume without loss of generality that a>b

clever pewter
#

yes

dark granite
#

Suppose the statement is false now

#

Then what happens

#

Think about what it means for the statement to be false

clever pewter
#

well it basically means what I said right

#

before

dark granite
#

Which was

clever pewter
#

a^2+b^2+1 != 3ab

dark granite
#

Right

clever pewter
#

or just a^2+b^2+1=kab with k != 3

dark granite
#

Exactly

#

Okay now let’s make that equation look like a quadratic in terms of a

#

So move kab to the left hand side

clever pewter
#

lol so my solution was not completely wrong

vale sapphire
#

Quickly jumping in to say that there is one case of inequality that can be very easily eliminated

clever pewter
#

attempt to sol*

dark granite
#

Yeah sounds like you weren’t too far off

clever pewter
#

x^2-(kb)x+b^2+1=0

#

with a as one of the 0es

dark granite
#

Nice

#

Yes

#

By Vietas formulas, what must the other root look like

dark granite
#

Look up em formulas yo

clever pewter
#

something like b^2+1/a?

dark granite
#

Right

#

And that equals another thing too

#

In terms of k

#

Kb-a

clever pewter
#

right

dark granite
clever pewter
#

(b^2+1)/a

dark granite
#

So this other root c equals bk-a and that fraction (b^2+1)/a

#

Is c an integer?

clever pewter
#

hmph

#

how do I judge

dark granite
#

What does c equal

#

Bk-a

#

Is that an integer

clever pewter
#

ok so a is an integer

#

and so is b

#

and so is k

#

so it has to be right

dark granite
#

Yes.

#

So now show c must be positive

#

Look at the other thing c equals for this

clever pewter
#

oh

#

(b^2+1)/a this should be positive right

dark granite
#

Yes but why

#

A and b are both positive right?

clever pewter
#

because a>b and b^2<a unless b is a natural number b<=1

dark granite
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Um all you need to show c is positive is the fact that a,b>0

clever pewter
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ah

dark granite
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So the numerator and denominator of that fraction must both be positive

clever pewter
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yes and we proved that it should be an integer from the other part

dark granite
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So c is a natural number

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Right?

clever pewter
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yes

dark granite
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Kk

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Remember when we assumed the statement was false?

clever pewter
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yea

dark granite
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Notice that we can also assume that there is a smallest pair of natural numbers a and b for which it’s false. We can define them to be the smallest pair by saying the product ab is smallest

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We’re allowed to do this by the well ordering principle

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We need to show know that cb <ab

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This will contradict the minimality of ab and finish the proof

clever pewter
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right

dark granite
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So using the fact that a>b and all we know about c, how can we show cb <ab?

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Hint:

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Show a^2>b^2+1

clever pewter
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ca=b^2+1

dark granite
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Right

clever pewter
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and a^2>b^2

dark granite
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Yes

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But that won’t help with showing a^2>b^2+1

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Since a>b, how can we relate a and b?

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Write a in terms of b

clever pewter
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hmph