#help-39
1 messages · Page 267 of 1
But R c R
Because R is a set
So we can also mark it as a set
{R} would be a set with the letter R in it
So it wouldn’t mean real numbers
Its like you dont say if A is a set , you dont say {A}
yes
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imagine a set would be a bag right?
so if you say {A}, it would be a bag containing a bag
But if A is alone then it’s okay?
Yep
if A is alone then it's just a bag
It’s like saying I’m eating unhealthy food and saying I’m eating a hamburger
Same for R
erm
I dont understand that concept but ig
yep, that's the issue
you'd be saying all unhealthy foods are hamburgers
R, the collection of all real numbers, is all the unhealthy foods
{R}, the single element, is one of the unhealthy foods
🤨
1 is not an element of {{1}}
because the only element in that set happens to be {1}, which is not the same as 1
but 1 is certainly an element of {1}
make of that what you will
no
use the bag thing i told you
{{1}} is a bag containing a bag which contains 1
we define $a \in R$ if the bag R contains an object a
1 divided by 0 equals Infinity
now we apply this to the set {{1}}
{{1}} has an object {1}
not 1
Only that
yep
Only {1}
yep
So it’s the same
?
"a bag containing the apple isn't the same as the apple"
no
Yes
@proper nova
are they talking about the problem now?
🙏
@civic drum hi
Yikes
use $\LaTeX$
1 divided by 0 equals Infinity

!noai
Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).
heyy
This exists precisely for cases like this
you’re so pretty
!redir
This channel is only for on-topic discussion. Please take casual conversation to #discussion or #chill.
you can complement your friend in there
She could’ve been more tanned
If R is a box, {R} is the box that contains the R-box
These are emphatically different objects
is this ragebait
you implying they know better?
💅 you're prettier!

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how would i go about this?
Ye, don’t advertise here
No ads.
you can integrate along the x-axis
to do that, you need to find the limits for the integral, and find the integrand
actually, a lot of the options have logarithms
so you should integrate along the y-axis instead
oh yeah, and it's also because there's dy rather than dx
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✅ Original question: #help-39 message
i tried doing that and keep getting the answer #4, which is apparently incorrect
4 seems right
Might be easier to do it for x and then do a substitution ig?
alright thank you guys, ill try it out again
i integrated w.r.t x and got the same answer
Yeah 4 seems to be correct
ahh, can i see how you did it to see if it's the same as mine?
<@&268886789983436800> troll
kil stab murder die
hello
anybody here studying for the december sat
and could help me with certain math problems?
this channel is occupied, pls see #❓how-to-get-help
👍
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hi
ahh yes nice legible drawing
abc and def are equilateral triangle
question: what is the ratio of the area of efcb vs dec
uh
compared to length
its square
4:9?
thats the answer?
yes
that was simple
wait
?
nope
def and abc
ratio between trapazoid efcb vs triangle dec
ok
both triangles are equalateral
yeah but
where is the second one
in relation to the larger
is it in the direct middle or not
oh
this seems like a very hard question imo
ok gn
Close the channel if yr doubt is cleared
i need help
What is the question?
here
Can't understand the question
same
Is the inner tri touching the outer tri?
idk
Ok
.close
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hey i wanna ask about something simple i really struggle with factoring my mind comprhend anything but that can anyone give me simple way to factor equation easily
yeah for example smthn simple like
x^2-4x+4
find a pair of numbers that multiplies to +4 and sum to -4
The best foolproof method: find roots of the eqn
Make use of quadratic formula
This is the most straightforward method
okay thank you guysss
That's the simplest
ill check it out
not fool proof by the way, consider x^4 - 27x^2 + 1
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id like to start with the second one
i dont understand how to approach a trig sub problem
like how to figure out what to sub in
i can sort of identify that this would be trig sub
but idk how to do it
Okay, multiply and divide it by 8 and then add and subtract 4
Separate out the 8x + 4 and -4
For the 8x + 4 fraction, u-sub denominator
wait
Sure
im not sure how/why you did this
Okay, so let me ask you something
If the question didn't have an x at the numerator, then would you be able to do this?
Okay do you know the formula for 1/sqrt(x² + a²)?
or wait
no
is that maybe arctan or something like that
No, that'd be just 1/(x² + a²)
How about we take x = atany
so its tan?
Okay see, $\frac{dx}{sqrt(x^2 + a^2)}$
doctorstrangejr
We're trying to integrate this
Take x = atany, it becomes $\frac{a(secy)^2dy}{asecy}$
but id like to know it off the top of my head
doctorstrangejr
Oooooo, well the formula I'll give you is in log, not hyperbolic function though
oh wow how do you end up in log form
its probably not necessary for me to know im curious but i should save it for another day i guess
Well we can just take it to be inverse hyperbolic sine then
I'm worried about the 'a' though, it won't be 1 here
Okay so basically, we can solve 1/sqrt(x² + a²)
So $\frac {xdx}{sqrt(4x^2 + 4x + 5)}$
doctorstrangejr
i understand so you used a trig identity to make it asecy? in the bottom?
That was for 1/sqrt(x² + a²)
Here we got a x in the numerator
So we gotta deal with that first
brb
right
so how do you try and do this?
u said multiply by top and bottom by 8 and then add/subtract 4
8xdx/8sqrt(4x^2+4x+5+4)-4?
Yes
So basically, what would be the differential of the function of the denominator in the root?
why do we take the derivative/
okay so what we're trying to do here, is get a constant in the denominator
is there a way to interpret this without memorizing the whole table?
whenever you've got a $\frac {(Ax + B)dx}{sqrt(Cx^2 + Dx + E)}$ type function
doctorstrangejr
You manipulate the numerator in such a way that you get two functions, where the linear function is basically the derivative of the quadratic in the denominaor's root, and the constant function can easily be solved using the formula of 1/sqrt(x^2 + a^2)
more intuition after one point if you do it a sufficient amount of times
So, taking your question
$\frac {xdx}{sqrt(4x^2 + 4x + 5)}$
doctorstrangejr
The derivative of the denominator is 8x + 4
So first we multiply/divide by 8
$\frac {8xdx}{8sqrt(4x^2 + 4x + 5)}$
doctorstrangejr
doctorstrangejr
Then we separate them
$\frac {(8x+4)dx}{8sqrt(4x^2 + 4x + 5)}$ - $\frac {4dx}{8sqrt(4x^2 + 4x + 5)}$
doctorstrangejr
i see
You basically u-sub the denominator in the first one and it's just $\frac {log(4x^2 + 4x + 5)}{8}$
doctorstrangejr
not sure how you get log there
Well just take $4x^2 + 4x + 5 = u$
doctorstrangejr
Post differentiation --> $(8x + 4)dx = du$
doctorstrangejr
oh wait
yeah you're right, I made an error
It'd be $\frac{du}{8sqrt(u)}$ not $\frac{du}{8u}$
doctorstrangejr
even if it was du/u itd be ln instead of log right
Eh I meant that only, but you're right, that's an important nuance
So now we can integrate this one
i see so this version of the problem doesnt require trig sub?
Not yet (also it completely doesn't if you remember some formulae, like 1/sqrt(x^2 + a^2)
Now here - $\frac {4dx}{8sqrt(4x^2 + 4x + 5)}$ (let's ignore the -1/2 for now)
doctorstrangejr
So simply $\frac {dx}{sqrt(4x^2 + 4x + 5)}$
doctorstrangejr
We break the quadratic in such a way that it's a sum/difference of squares, where one is a function of x and the other is a constant
Now $4x^2 + 4x + 5 = (2x+1)^2 + sqrt(3)^2$
doctorstrangejr
doctorstrangejr
Now firstly we'll take (2x + 1) as t to remove any constant multiplied to x
so $(2x + 1) = t$
doctorstrangejr
Alternatively, instead of doing this headache, we can just take 4 common here and bring it out of the root as 2
So $\frac {dx}{2sqrt(x^2 + x + 5/4)}$
doctorstrangejr
doctorstrangejr
You following me so far?
yes
Okay
Factoring where?
here
Okay so a trick is
Like I had 4x^2 yes
And there's only one x function after factoring (ax + b)² ± c²
So 'a' I can simply find by the root of the x² function (which is 2 here)
For b, once I have a, I just look at the x term I had, because that term would be 2ab
And that term I know, so 2ab = [term of x]
Here we can find b
Now whole square it, and by whichever value the constant is off, the root of that is c
For eg, $(9x^2 + 10x + 60)$
doctorstrangejr
Holy it's getting on my nerve
Okay so here we find it in terms of (ax ± b)² ± c²
a²x² is just 9x², so a is 3
(3x + b)² is 9x² + b² + 6xb
6xb = 10x
b = 5/3
Now b² is 25/9
And we need 60
So sqrt(60 - 25/9) is c
Seems like a lot but when you do it, it makes a lot more sense
it does seem like a lot
Calculate this (m+)
it does make sense
It's that kind of a thing, you can do it quickly but explaining/understanding it for the first time takes a lot of time
?
Okay so our integral was $\frac{dx}{sqrt(x^2 + x + 5/4)}$
doctorstrangejr
yep
x² + x + 5/4 = (x + 1/2)² + 1
(See how I do it so fast, it's really simple once you get it)
That makes it $\frac{dx}{sqrt((x + 1/2)^2 + 1^2)}$
doctorstrangejr
do you go through all the steps in your head?
In a way, although I do need to see it written, otherwise it becomes a mess in the head
Now the integral of 1/sqrt(x² + a²) is log(sqrt(x² + a²) + x)
So it simply becomes log(sqrt(x² + x + 5/4) + x)
Now add the constants, and that's your integral
im not entirely sure if thats equivalent though
shouldnt the original expression on the denominator (sqrt4x^2 +4x+5) be in the final answer somewhere
oh but maybe once the constant distributes
But we did have sqrt(x² + x + 5/4)
It's more about familiarity
I saw the integral and instantly knew what to do, after some practise you would too
i need to study all night i have a lot of sets of problems to sort of get down
Well practise is a virtue man, the more you practise the better you get
are volumes and areas easier, we only have to create the integral not solve it
like areas between curves and volume mostly cross sections and rotated about some axis
yep
Ahhh yeah that could be a headache too
However it depends on the level of questions you have
what makes these hard?
I mean just the visualisation
And you gotta know the concepts well enough in case you're ever confused somewhere
not sure what makes these hard to visualize i mean i think x^3 and 4x is pretty simple to look at
@soft otter Has your question been resolved?
Yes
and i made it into (u^2 -1) root 4 u du
u=e^x +1
oh wait
i made a fatal algebra mistake
oh ok does that work
Well, open the whole square
Then multiply each term with u¼
Then integrate all 3 of them individually
Nice
id do
u^4 = e^x + 1
it simplifies to something quite nice
just the power rule
ooooh
believe it or not
just set the denominator equal to u
because youll get constant + sec^2x
which is very similar to the numerator
yeah i think i got it
if you differentiate the denominator, then multiply by some constant, you get exactly the numerator
i just multiplied by 2
how do u take 2 out?
ah
Is yr doubt solved?
Hi! The easiest way to do this question is to show by example that g(x) has no inverse function.
Under what circumstance does a function have an inverse function?
one to one
Good! So,
Try and show that this function is not one-to-one. That is, can you think of two values of x that have the same output?
Perfect! That's it.
When x = 0 and x = 1, the function values output to the same thing. So, the function does not have an inverse on R.
if i had to show f(x) was an inverse function how would i do that
the e term is confusing
Hint: Consider the derivative of f(x).
What can you say about the derivative? (Specifically, what can you say about its sign?)
Positive?
Good! (Well, you need to show me that in your working :) )
Now, if f'(x) is always positive, what does that imply?
since its always increasing it will be one to one
but how would i find the inverse function if i could
Yep!
That's a more interesting question
Don't think it is possible here algebraically
Best thing you can do is swap x and y.
i see
@soft otter Has your question been resolved?
@soft otter Has your question been resolved?
How far have you come?
In these types of problems, a good starting point is trying to find a counter example for the statements
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Can anyone help me with this shii?
Is there anyone here?
@pastel mango just calculate A, A square and A cube
I think factoring like that makes it easier personally
Afterwards write 2 as the unit matrix times 2 and then add componentwise
The problem is, if I subtract 2 from the Matrix A, what would the result be 😅
@pastel mango .
Alr but, a pic would help me a lot 🥲
Ouuu
This case we use $I_3$. Sorry I do not know how to typeset matrices in laTex
Adhi
,, X=X\cdot I_n=\begin{bmatrix}x&0&\cdots&0\0&x&\cdots&0\\vdots&\vdots&\ddots&\vdots\0&0&\cdots&x\end{bmatrix}
ΠαϳαμαΜαμαΛλαμα
thanks man
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Lesson 8: Find m so that the inequality mx – 3m + 2 > 0 has x > 0 as its solution
Lesson 9: Find m so that the inequality x + m ≥ 1 has x ≥ -2 as its solution
Lesson 10: Find m so that the inequality 2x – m < 3(x – 1) has x > 4 as its solution
can someone help me pls, i'm new to inequality
I need the answer, I'm new to inequality
Have you done something similar in class? There are basically two ways of doing this; purely algebraically or geometrically visualizing it
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
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On what basis is the highlighted step done ?
the question specifies that this angle must be acute
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hi, i have this law of composition and i need to prove its an abelian group
i got trough all axioms but i dont understand commutativity
i get to x^{\ln y} = y^{\ln x}
WTF
i know if i take ln of both sides they are equal but is that the correct way to do it?
yes
Wait, just to be rigorous to the formatting, you should start with the expression
x * y = x^ln(y)
Then taking the natural log of both sides.
The point is, you want to show that ||ln(x * y) = ln(y * x)||, then use this to show that the group is abelian.
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I personally think the more important point is that ln(x) is one-to-one.
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I don’t understand for b
!occupied
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have you made a diagram?
please claim your own channel
#❓how-to-get-help for instructions
@burnt skiff you there?
right ok so you've done part a right
so you know that vector GG' = GB + GC
do you also know the vector sum GA+GB+GC = 0?
@burnt skiff Has your question been resolved?
consider that G'A = G'G + GA and likewise for B and C
and G'G = -GG'
my idea actually was that you could first just add all three together
and get G'A + G'B + G'C = 3 * G'G
Don t you have a full demonstration I’m quite sure my small brain won’t put piece to piece bits of information
i'd rather not give away the full solution, no.
Then maybe elaborate ?
A line
So I understand
I don’t know what bumble jumble you are trying to prove
I found another solution
Thank you ☺️
.close
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can someone help me here
im not understanding what hes doing here
this is a weird notation, i dont understand how he calculats with it
seems like a kind of ratio test to me
What do you not understand? The algebra? Or why he did what he did?
the algebra
only the algebra
the generall idea i completly understand
but i never seen it writen like this 13....*(2n+1) and i never calculated with it
It's the product of the first n + 1 odd numbers
It'd probably be better if you rewrote in terms of factorials and exponents: $1 \cdot 3 \cdot 5 \cdots (2n + 1) = \frac{(2n+1)!}{n!2^n}$.
jewels!
(That should make the ratio test easier to apply now)
is this the whole term
No just the denominator inside the square
jewels!
not getting this
Try on small examples
$2\cdot4\cdot6\cdot8\cdot10=\left(2\cdot1\right)\cdot\left(2\cdot2\right)\cdot\left(2\cdot3\right)\cdot\left(2\cdot4\right)\cdot\left(2\cdot5\right)=\left(2\cdot2\cdot2\cdot2\cdot2\right)\cdot\left(1\cdot2\cdot3\cdot4\cdot5\right)=2^{5}\cdot\left(1\cdot2\cdot3\cdot4\cdot5\right)$
MathIsAlwaysRight
Factor all the 2s out
not all of them, just one 2 from each factor
in the product 2 * 4 * 6 * ... * 2n there are n factors and each one can have a 2 extracted from it
when you do that to all of them and put all those extracted 2's on the left you get 2^n * (1 * 2 * 3 * ... * n)
does that make sense to you
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hi I was just wondering if I can find a series representation by manipulating this function
But I think something is not right lol
It’s not matching the answer, and im not really sure with my integration tbh
what’s going on in the first 3 lines?
You sure that you are differentiating correctly?
equal signs don’t make sense there
It seems like they integrated instead
Kinda but even then
I think you're better off starting with $\frac{1}{1 - x} = \sum_{n \geq 0} x^n$, and manipulating both sides to get what you want
jewels!
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why it is hard to find sources which write clearly about second linear differential equation. Can someone suggest me please?
@calm pike Has your question been resolved?
@calm pike Has your question been resolved?
Khan academy is always a good go to
Also "Paul's online math notes", I believe
Even though honestly I don't remember if they cover diff eq as well
yah but in this section Paul not attach practice...
This isn't a math question. Just go Google resources and books
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This doesn't appear to be orthonormal. <x,x> = 0 for rho2, rho3, rho4, rho5
My calculations may be wrong.
<p2,p2> = 1 + 7z + 7z^2 + 3 + 3 = 7(1 + z + z^2) = 7(0) = 0
<p4,p4> = 9 + 3(-3) = 0
Should be (21 without normalisation) 1 for both of these.
Thanks
Fair - I thought I was just being blinded by the fact it's 4am
Ahah
chatgpt is often wrong
Don't think that's really in the spirit of this channel 😆
Fair though. Bedtime
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✅ Original question: #help-39 message
@unique viper Has your question been resolved?
What's your question? And also, which representative have you picked for that semidirect product?
The character table aligns with one I was given for a question
The rows do not appear to be orthonormal (see my working) wrt the standard character inner product.
My question is: is my working wrong?
For reference,
21<p1,p1> = 1 + 3*1 + 3*1 + 7*1 + 7*1 = 21
Which is what we want for <p2,p2> etc.
We also want <pi,pj> = 0 for i =/= j
Which course is this problem in? Because, while I'm familiar with that semidirect product, I don't recall it being endowed with an inner product or a notion of normality
At least, not when I saw it
Representation theory
Hm, might not be able to help you then, not too well versed in that discipline, apologies
An example of a table which works is here - this is the character table of S3
<V,V> = 4 + 2*1 = 6
<V,1> = 2 - 2*(-1) = 0
etc.
Not only that, but the columns should be orthonormal wrt the standard dot product
works here
not here
No worries - could you point me towards a channel which could help? Thinking of #advanced-algebra but that's not quite rep. theory
If I remember correctly, that's the channel used for representation theory, yeah
If not, you can also try in #groups-rings-fields , maybe you'll have more luck there
Thank you
Np, hope someone can help you
I'll ask there and go to bed
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hello
i’m trying to determine whether this function under Z -> Z is injective, surjective or bijective
so the correct solution i was given is that it’s not injective but it is surjective
have you considered whether it is in fact a function at all
hm
what would be better to write?
"f is injective"
i see
can you send the original problem btw
ofc
i wanna make sure there's no misread bullshit
oh well you went and obliterated the floor function brackets.
that does NOT pass the horizontal line test
Ann
OH
that was a floor function? i didn’t even realize that 💀
we are rounding to the smallest integer number
@frosty grail Has your question been resolved?
i mean you kinda have to understand how it works on a deeper level than pushing symbols around
like floor(n/2) should clue you in that maybe it behaves in some significant way on the odd numbers vs the even numbers
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@elfin geyser Has your question been resolved?
<@&286206848099549185>
@elfin geyser Has your question been resolved?
<@&286206848099549185>
i don't really know what i'm looking at but you should have the equation
[ s^2 X(s) - sx(0) - x(0) + 4X(s) = \frac{e^{-2s}}{s} ]
where i think the part you need help with is the RHS?
THERMOONUCLEAR BOMB
or needed
with the initial values we have $$(s^2 + 4)X(s) - 2 = \frac{e^{-2s}}{s}$$ so $$X(s) = \frac{2}{s^2 + 4} + \frac{e^{-2s}}{s^3 + 4s}$$
THERMOONUCLEAR BOMB
the first part of the rhs on the second eq is clear
i think you have it from here?
@elfin geyser
I am confused because according to the second shift theorem, this is the transform of the heaviside function, but is f(t-a) just 1?
yah, exactly
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close enough
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On the BC side of triangle ABC, point D is taken so that BD/AB = DC/AC. Prove that AD is the bisector of triangle ABС
hold up
What can we use? are trigs allowed?
congruency alone won't solve this
Only basic ones. Sin, cos, tg
angle measures
.
How did u find this
i drew my own diagram on geogebra
your measures might be different
well there arent any measures
triangle is arbitrary
won't it?
since the third side is common
AD you mean?
yeah
how does a triangle which has full acute angle
congruent to a triangle which has 1 obtuse angle
explain
AB/BD=AC/DC=AD/AD=1
no angles have been given
which it isn't
then draw a diagram, and look using your eyes
extend AB, E is in AB so that AE=AC
This's a big big hint
Reason behind it is because we are given BD/AB=DC/AC
It looks like SAS case in similar triangles
no ratios have been given 1 which is according to your logic
$\frac{BD}{AB}=\frac{DC}{AC}=\frac{BD+DC}{AB+AC}$
Alexis_Fx
oh shit i forgot the two ratios are not equal to AD/AD my bad
i just assumed they were, without realising there's no reason for that
bruh wait I meant SAS
@indigo stone Has your question been resolved?
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Let $v$ be an eignvector of $T$. Then $T(v)= \lambda v$. $\phi(T(v))= \lambda \phi(v)$]
wai
(xristina spam)
I suppose what I did was wrong?
I mean it didn't get you anywhere useful that I can see
yea
I need to start with an eigenbasis and assume F=C
idt this is doable in F=R
ykw I'll do this tomorrow
I'm too sick ( atually) to do this anymore
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wait I just use the isomorphism b/w V and V'?
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i have 2 equations: x + y = 50 and xy = 87, i need to solve for x and y in simplest form(not fraction) what i'vev done is made new equation, y = 50 - x and then substituted for y, x(50 - x) and then simplified, 50x - x^2 = 87, last i made it a quadratic equation, 50x - x^2 - 87 = 0 but i dont know how to finish with the formula, i do know it is: -b +or- sqrt(b^2 + 41c)/2a but cant figure out what a b c is
so what is a b c i can do the formula by meselfbut cant figure what a b c is
You can just help yenno
now can you see what a, b and c are?
Sorry I was helping another person
i do know it is: -b +or- sqrt(b^2 + 41c)/2a
this is badly written
also actually incorrect
the stuff under the root is b^2 - 4ac and not b^2 + 41c
i meant to do 4ac
Then stop spamming everywhere and just help
and then also brackets
what do you think I am doing
.
well yk I have 12 other tickets too
so im replying to this guy then this
Spamming "I'm here to help" in 10+ channels is not useful.
Well I am letting them know
So they do not go afk
You're just flooding their channel instead of helping. Stop
apparently i blocked this guy but i have no recollection of what for
You're not the only helper here 😅 there are at least 20 online I believe
Ohh that explains it
ok actually what is the value of a b c
ok let me help
rearrange it so the terms are in descending degree order
-x^2 + 50x - 87 = 0
let me solve the equation
Ok I’ve solved it
no
a, b and c never involve x themselves
b is just 50, not 50x
a is -1, not -x^2
A is -1 and b is 50 c, -87
why is a = -1 from -x^2
Oh Mb it’d -87
-x^2 = (-1)x^2
$$ax² \quad \quad -x²$$
Alberto Z.
oke
oh
so a = -1, b = 50 and c = -87
got it
so finally sub each value to get ansewr: $-50 + $sqrt($50^2 - 4*$-1*$87) &/ &2*-2
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Hi! I'm trying to find out how many digits 2^n has, I've kinda played around and got the ceiling of log_10 2^k, would this be the expected answer?
digit count of N generally equals floor(log_10(N))+1, but for all n that aren't perfect powers of ten this does match up with ceil(log_10(n))
so powers of two are not very special aside from never coinciding with powers of 10
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i need help with number theory especialyl modular airthmetic i dont understnad a thing
what is multiplicative inverse
we say b is the multiplicative inverse of a if a x b = 1
So for example in mod 5, multiplicative inverse of 3 is 2. Because 3 * 2 = 6 = 1 (mod 5)
where 1 is the multiplicative identity
is mod just like base. so mod 5 is base 5
absolutely not
Not at all
no like the digits they use no?
I see what you are thinking here
before I try to explain this
what level of math are you at
mathcounts middle school competition
oh lol
okay then
as a simplified explanation
just think of a mod b as the remainder of a when divided by b
if we take the number 10 and divide it by 7, we get 1 and a remainder of 3
so 10 mod 7 = 3
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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
@coral jackal Has your question been resolved?
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This is what I have rn
but epsilon1 is supposed to be greater than 0
which rn my two solutions are not
is this supposed to be your proof, or are you just doing work to figure out how to write it?
You can avoid this by assuming additionally that delta is less than 1
trying to write the proof
altho I've found myself stuck
not sure what thatd do tho? can't seem to get any part into |x-4|
Oh sorry I misread
Okay so you can do |f(x) - 7| < 1 whenever 0 < |x-4| < some delta’
So with ur delta_1 from
before, choose delta = min(delta_1, delta’)
Obviously you should probably use some other notation if you’d like for this delta’
But notice what this lets you do
@fair comet lmk if that’s unclear or not
Sorry saying to choose delta this way is obviously wrong since you want to find it, but hopefully it’s clear how you can find it now
I don't think this is what you meant but I think it works?
Hm, not clear what happens here for me
Could you try and point out what youre doing
And why
if I choose epsilon1 to be the min of 1 and epsilon/16 then
for epsilon1=1 then 6<f(x)<8
plugging in upper bound of 8 for f(x) and epsilon/16 reduces to epsilon which proves the limit?
I'm not entirely sure if I can choose epsilon to be multiple values the way you can with delta tbh
I see that looks good
You should preferable instead do this from the choice of delta, i.e you know e.g. that there’s delta_1 such that |f(x) -7| < 1, and there’s delta_2 such that |f(x) - 7| < e/16 whenever 0 < |x-4| < delta_1 and delta_2 , i.e whenever 0 < |x - 4| < min(delta_1, delta_2)
right that makes sense, but the issue is I don't know how to use delta in my proof as I can't get any part to be in terms of |x-4|
I might be missing something really obvious I'm not sure
That’s fine
You don’t have to
You know how to bound |f(x) - 7| and that’s enough
Try and write it all up formally
And notice you’ve done exactly what was needed for the definition of a limit
I’d argue a bit differently for how to bound |f(x) + 8| since you already set that up before nicely imo
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did you see my message from last time
Yes
But I don’t rlly see how that helps in solving this
I get that it’s derivative is this graph given here
mhm
What can you say about $g$ being increasing/decreasing on each of $(a,c)$ and $(c,b)$?
Civil Service Pigeon
@coral jackal Has your question been resolved?
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$r={ (x,y) \in \mathbb{R}^2 \mid y=tx^2+8x+10-t, t \in \mathbb{R}}, {A = {t,$ where t makes R_r \subset \mathbb{R}+}$. B=(-2,4). Find A' \cap B.
R_r is defined as the range of function r
What is A prime?
d1 shitposter
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defined as the complement of A
all R not A
computed t to be the real numbers ranged (2,8)
$r={ (x,y) \in \mathbb{R}^{2} | y=tx^{2}+8x+10-t, t \in \mathbb{R} }, A = {t ,$ where $R_{r} \subset \mathbb{R} }$. $B=(-2,4)$. Find $A^{c} \cap B$.
so A' would become R-(2,8)
Cogwheels of the mind
$y=t((x+\frac{4}{t})^{2}+\frac{10-t}{t}-\frac{16}{t^{2}})$
Cogwheels of the mind
R^+ is positive reals or non-negative reals?
pretty sure it's positive reals
includes zero
?
Anyway, I got A=[2,8] / (2,8) depending on R^{+} include or not include 0
Okay
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What do we mean by this?
which one?
yea
ur right that for each fixed c that funciton is a straight line
but
16
what i assume ur confused on is the point of the exercise is to check its a solution
no i am kinda confused that this differential equation has a straight line as one of its solution, which feels kinda counter intuitive?
and the graph
theres nothing that says a differential equation cant have straight lines as solutiuons
the straight lines are just the slopes of the parabola y=x^2/4
which is also a solution of this differential equation
i mean yeah thats true
i think ill focus on this, is there a connection/relation/anything why the slopes of the solution are also the solution to this equation?
yea if u solve the DE for y you get y = xy' - (y')^2 so it literally says the solution curve must lie on one of the lines y = mx - m^2 which is why those straight lines and their envelope y = x^2/4 all satisfy it