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A horizontal rectangle of rectangular cross-section
beam in the vertical direction is directly proportional to the
the product of its width and height in cubic form, i.e. it is of the form cxy3,
where c > 0 is a constant. Determine the width and height of the stiffest possible beam when it is
sawn from an R-beam log.
Im not really sure where I should start with solving this.
Its from my calculus class
@wooden mantle Has your question been resolved?
<@&286206848099549185>
nope, this is the whole question, I translated from Finnish to english
wait It should be (xy^3)^2
lemme fix that
oof
thats what I mean, like how do I actually go about solving it 💀
I mean I can't understand the problem at all
I think we need to maximize one thing subject to some constraint
Like, maximize cxy³ when xy=R or something except that doesn't even have a solution so idk
Yeah the question is so abstract imo
Im not sure what you mean
This is prob easier to understand if I draw something gimme a sec
like this
aint they just asking the length and height of the cross sectional beam when at its highest possible stiffness
But like
It can be anything since we dont have actual numerical values right?
Yeah no clue
"Determine the width and height of the stiffest possible beam when it is
sawn from an R-beam log."
No clue what an R beam log is either lol
I found something similar
Radius of the log
I mean I think I understand it better niw
ah that's good
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Np!
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here is a question I got wrong on a test. Can someone show me how to do it properly? Simplify $\frac{x^{2}-16}{x^{2}-3x-4}$
PeckyChicken
Can you show what you did on the test?
$4 - \frac{1}{3x}$
PeckyChicken
I'm more talking about the steps leading up to whatever final answer you get
I have 0 idea where you went wrong just by looking at this
I went wrong by assuming you could just take the 2 x²'s out of the fraction
leaving $\frac{-16}{-3x-4}$
PeckyChicken
I think
Fair enough
Do you know how to factor quadratics? Because ideally, once you factor both sides of the fraction, they'll have a common term you can cancel
yes 🤦
top is a difference of 2 squares
Ok well then factor them 
so $\frac{(x-4)(x+4)}{(x-4)(x+1)}$
Hey look, a common factor
$\frac{x+4}{x+1}$
Quite so
on the test answer it says x +4/x +1. I dont know how to parse that
I shouldn't have given the go-ahead so fast
PeckyChicken
Better
PeckyChicken
that matches the answer on the test
Very nice
may I close the channel?
You don't need my permission
also
If you have nothing else, close whenever
this
should not have come from this either
wait I see what i did
I extracted the -16 and the -4

I extracted -16 and -4 which gave me $\frac{x^2}{x^2-3x}+\frac{-16}{-4}$
PeckyChicken
you totally cant do that
yes ik now
good
They have since found enlightenment
amazing

then my next step was to extract the $x^2$. $\frac{x^2}{x^2} + \frac{1}{-3x} + 4$
PeckyChicken
and you can see how i ended up with my answer there
mathematics if it was different

on another question i gave the answer $\frac{x-1}{2}$. The correct answer was $\frac{1}{2}(x-1)$. They are the same right?
PeckyChicken
Indeed
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how do I solve
un+1 = 2un - 1, u1=2 for n>= 1
Find the term that has value 257
n+1 is in subscript
and n
in the 2un
And also 1 in the u1=2
I tried doing it by substituting values
But i could only find answer by listing all the values manually
Is there a simpler way
and how do I solve this
un+1 = 3un - 2, u1=2 for n>= 1
Find the value of the largest-term that is less rhan 10,000
try to find the general term
yeh
I was thinking of doing that when i realized one was geometric and one was quadratic
But in the tb, they didnt cover general formulas yet
So i thought there was another way
@radiant karma Has your question been resolved?
<@&286206848099549185>
@radiant karma Has your question been resolved?
@radiant karma Has your question been resolved?
@radiant karma Has your question been resolved?
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Hello, I'm struggling with this scaling issue in my code.
I thought multiplying C's X,Y by scale would put it in the right spot.
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how would i solve this?
(x+8)^2+(y-4)^2=144
get the circumfrence
are you able to identify the radius?
how would i do that
compare this to the general equation of a circle in standard form
that will tell you where radius is located in that equation
ok
@alpine sable Has your question been resolved?
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i just need to know how this problem is named, like, connecting dots with lines, then adding a dot
I don't understand what you mean. Given a set of points, adding a line between every pair and then adding a new point and connecting it with any of the previous ones?
graph
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i need an answer and also an explanation, please
@devout zinc Has your question been resolved?
<@&286206848099549185>
It's one dimensional so it only has length?
well, it must have thickness right
if we use a microscope or smth we might be able to see the thickness
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"Determine λ ∈ ℂ such that the quadratic equation has two opposite roots." I've tried multiple times (abc formula) but keep getting wrong answers. Could someone help me out?
with opposite you mean a+bi and a-bi?
yeah the quadratic equation (even the complex version) doesnt really work that well when complex a,b and c
you need to "kwadraat afsplitsen"
dont know the english term
no, a+bi and -a-bi
ah ok
ow, I'll try searching that up. thanks!!
.close
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I need help with question number 2, 3 and 4. I've provided 1 because question 3 requires it. I don't understand what it means by **standard factor ** on question 2. Thanks
alright what about question 4. could you explain what it means by the question please?
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You are voting in a state election. There are three candidates for governor, five candidates for lieutenant governor, four candidates for the state house of representatives, and two candidates for senator. How many different ways could you fill out the ballot if you vote once for each office?
yeah ik
i think u just multiply all the numbers
i agree for once
you've been saying some sus things tonite 

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This is probably a very easy quotation but how would you find a percentage of a total when the components of that total is weighed differently. So like in my case, 17 of the total 24 is weighed at .8%, but the other 7 is weighed at .3%. How can I find the average percent for the total? I phrased this very poorly but
Basically like the average percent of the total 24 if 17 is multiplied by .8% but 7 is multiplied by .3%
@hollow fjord Has your question been resolved?
@hollow fjord Has your question been resolved?
@hollow fjord Has your question been resolved?
@hollow fjord If I interpret your question correctly, I think you're looking for a weighted average. In this case you would need to sum all the amounts multiplied by their corresponding weight factor. Then divide that by the total amount
So you would have $\frac{17 \times .8 + 7 \times .3}{24} = .654...$
joshy
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hi
could i get help in solving this, the answer is -1/2 according to the textbook but i'm not sure how to get there
from my knowledge of limits, i would usually multiply the reciprocal of the denominator on the bottom and top, but in this case theres a second part to the function, that being - 1/t
Try combining the fractions into one
would that be the only method?
$\frac{1}{t\sqrt{1+t}} - \frac{1}{t}\ = \frac{1}{t\sqrt{1+t}} - \frac{\sqrt{1+t}}{t\sqrt{1+t}}\ = \frac{1-\sqrt{1+t}}{t\sqrt{1+t}}$
Kaisheng21
@royal meadow i understand that, but im not sure what to do after
i plugged in zero and got zerro
well if you just try and plug t = 0 right in, then you get 0/0 right
yeah yeah
so it's indeterminate
so you can try l'hopital, or use taylor series if l'hopital isn't allowed
my problem is i dont know how to simplify that fraction, after getting 0/0
well i don't think you can straight-up cancel any factors
yeah
you need some calculus to deal with the limit
so try l'hopital, or taylor series if that's not allowed
What if you multiply the top and bottom by √(1 + t)?
is thta possible?
oh yeah that's slightly simpler
yeah
it doesn't solve it but it helps a bit
$\frac{\sqrt{1+t} - 1 - t}{t(1+t)}$
ive been doing that for everything else but since there was a - 1/t i thought it wasnt possible
Kaisheng21
i wish it wasn't so big
can you??
i mean that gives like

if you divide top and bottom by 1+t?
Fuck it, let me get some paper
is that what you're saying?
Basically, yeah
ok
so we just multiplied top and bottom by sqrt(1+t)
and now you want to divide top and bottom by (1+t)
I'm probably high
that's the same as just dividing top and bottom by sqrt(1+t) in the first place
i don't think that works
my advice is try l'hopital or taylor series on this thing
very very bad advice
lets not go there shall we
you know the saying
when you have a hammer
everything starts looking like a nail
There's gotta be some way to get rid of the t in the denominator
factor out the t from the denominator
But then you have a 1/0
this is why we arent finished yet
does that actually help
how
We're back to this
where did everyone's algebra skills go
I'm racking my brain jimbo
😶
the t on the numerator cancels with the t outside the brackets
FUCK
I was high all along
ah, ok
I just helped someone with a problem where you do that exact thing like 5 seconds ago 
bluh
L'H is a hammer that is almost always not needed
some sets of problems are meant to be done without it
Using l'h is like using a graphing calculator instead of u sub, integration by parts, trig subs, etc
and it was much simpler
sure
you are going around nuking everything
when a simple knife couldve done
If you use l'h on every limit you come across that's of the form 0/0, you'll never learn the actual methods for limits
Limits
mhm
Not integration
agree with dio
well
and that's why i choose to use L'H's
it seems you dont
because they're awful
yeah yeah yeah
that's fair
fine, i'll rephrase
i know the other methods for doing limits
so i use L'H's because i suck at them
easy
It's like using the quadratic formula on an easily factorable quadratic
perfectly valid
you suck at them because you rely on L'H
no kill like overkill
i do ^-^
i would like to give people better advice
ok fine
i didn't spot the algebra
it was square roots
i should remember square roots are often algebra
Alright I got it now
not L'H's
thanks guys
yw
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can I get some help?
So I have a multistep problem, I have done all of it I just need to solve the equation
this is the problem: Lydia inherited a sum of money. She split it into five equal parts. She invested three parts of the money in a high-interest bank account which added 10% to the value. She placed the rest of her inheritance plus $500 in the stock market but lost 20% on that money. If the two accounts end up with exactly the same amount of money in them, how much did she inherit?
I need to solve this but I don't know how
You can write left as (3x/5) * 1.1 and right as (2x/5-500) * 0.8
Like this?
Yeah
how come?
because I multiplied it by 3, but I asummed because it's a variable you couldn't do that
Just the way my teacher taught me I guess
but I did get the initial equation right, correct? I am doing this for extra credit so I really want to get this right.
wdym
Well i don't know how you find that
I have the question above so I tried writing out an equation
This is what you have right?
yeah, that should be the equation for this problem
x being the inheritance
I needed to split the it in 5 parts take 3 of those 5 parts and add 10% of its value to it and then for the second parts and $500 in a stock market and lost 20% of it
my teacher said each side should be equal
I think it is right because I asked my teacher for help when I was doing this in class and she never mentioned my equation being wrong
Well alright
I don't get it though
The right part is (2x/5+500) * (0,2-1) = (2x/5+500) * (-0.8)
Isn't that negative?
which part?
the right part
sorry I'm confused its been a long day
This won't take long but i think you do not have the right equation
what did I do wrong
It's (2x/5-500) * 0.8 instead of (2x/5-500) * (-0.8)
So it should be -(x/5...)*0.2 + (x/5...)
instead of +(x/5...)*0.2 - (x/5...)
Still right part
she has 100% of the money
- (x/5...)
She loses 20%
-(x/5...)*0.2
If she has 10$ and loses 2$ she has 10-2 not 2-10 can we agree on that?
yes
yes
that makes sense
sure
so what would I do next? combined like terms?
You need to factorize
I don't want to sound stupid, but what is that I haven't learned that yet
Well i can't explain it very nicely because i'm not an english native so you should check with google
But basically it's the way of writing ax+bx=x(a+b), you find a common factor (this time x) and you can write it like this
2 * 4+2 * 1 = 2 * (4+1)
okay, so how would that apply here? Would I have to do 6x/5 x 0.1
that would be one side
but the * 1 doesn't do anything so why add it?
Why not
In the example 2 * 4+2 * 1 = 2 * (4+1)
You can explain 2 * 4 + 2 = 2 * 5
(3x/5) * 0.1 + (3x/5) * 1 = (3x/5) (1+0.1)= (3x/5) * 1.1
I think I get it
maybe not as well to do it by myself but I understand what your doing
yeah I'm not sure of the first step sorry
I have to add a * 1 so I can multiple something to both sides?
then add them?
yes then combined it into (2x/5) * 1.2?
you can factor (2x/5+500)
oh I forgot about the +500
(2x/5+500) * 1 - (2x/5+500) * 0.2 = (2x/5+500) * [1-0.2]
subtract the 1 and the 0.2 because in we needed to subtract for the money in the orginal problem correct?
not really
Well let's put that aside for now
In the end you have (3x/5) * 1.1 = (2x/5-500) * 0.8
I have to go in 4 minutes so I don't really think we can do that much right now but this was the other side?
thank you so much
sure
whats 8 + 11
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@keen plinth are u alive? i wanna ask some meth
yeah do that
so a linear transformation is when we transform the entire x/y/z... axis and make sure that
- origin remains the same
- all the grids' lines must be straight
so for linear trans, we can imagine it as a function taking in a vector and returning as a vector
so here, vector i (1,0) gets multiplied by -1 so it on the left now
then vector j gets multiplied by 2 which extends it by 2
i seriously dont understand this linear transformation
what made it such that the axis needs to look like this
this is just a representation of a vector
so a vector in 2d has 2 components
the i component and the j component
we write it like the column vector
yes
that just signifies its components in the i and j directions
the thing about linear transformations is
you only need to know where they send i and j
because you can rebuild your vector from knowing how much of the i component and j component it has
hmm ok
but why like this
why turn the whole plane that way
is it because of the values put in
thats just a specific example of a linear transformation
nothing particularly special about it
oh so i can rotate the plane to any way i want
yes
yes
waitbut whats the point of doing that
isnt visualising on the regular plane much more easier
what do you mean
like why not use this normal plane
whats the use of doing a linear transofmration
making the plane look so weird
well the thing is
we start with the standard cartesian plane
but
we want to apply a transformation to it
if we start with the standard cartesian plane and we change it
it necessarily gets wonky
you cant change something and still stay the same
thats kinda paradoxical
well
thats what the study of linear transformations is about
linear transformations are exactly those things that change the cartesian plane in this way
the whole of linear algebra is this
every single matrix youve looked at
does this
like we can have the most complex matrix and we can still use the original cartesian plane
wait the linear transformation is the transformation of the plane right
not the resulting vector
yeah
how does a matrix determine how the plane will look like
i thought we can choose not to cchange the plane
keep watching?
oh
has it been explained yet?
he explains at some point that the columns of a matrix correspond exactly to where i and j are sent
wait so we can do this because
ye he did
yeah
heh wait wut
because v is just 2 numbers
its how much i it has and how much j it has
the linear transformation changes i and j
so v changes along with
wait so that changes the vecotr
not the plane
like if i is (1,0) and j is (0,1)
lets say i multiply i and j by 2
the point is that its basically the same thing
then
its columns tell you where i and j go
like lets say i change the values of i and j
ok lemme draw it out
is this right?
no that’s transformation 
then this would be how its represented in the matrix form
wat
im so confused
AAAAAAAAAAAAA
yes
except like
you havent changed anything lol
but yes thats right
so the first column stands for the x coords
and second for y
then lets say i wanna multiply the scalar 2 to both x and y
green is aftermath
yea so the matrix will look like
2,2
so 2,2 is the vector of the resulting vector right?
which is the orange line
uh

umm wym
that vector
yeah
you have to apply a linear transformation to a vector
to get out a new vector
otherwise you just have a linear transformation
yeah
HEH
this is an example of where [x y] is sent
um where did this come from
try it for urself
what that not correct
nani wat that
?
im talking about the green vectors here
like this one is the final vector cant we represent it in (2,2)
oh
oh lmao
like
your linear transformation turns the red i, j into the green i, j
so its the 2 0 0 2 thing
\begin{bmatrix}
0 & 2 \
2 & 0
\end{bmatrix}
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
this
thats what u looking for
green one
the i and j just get scaled
i dont even know what deep is talking about anymore

wait how did u get this
ye
uhh 
this is a reflection
in the y=x line
and also scaling up by 2
wait so a linear transformation is it the transformation of the ENTIRE PLANE or just the vectors
or do the vectors determine how the plane looks
its a function that takes in vectors and spits out vectors
you can think of it as transforming the ENTIRE PLANE
but really you only need to know where i and j are sent
because every other vector can be expressed in terms of i and j
wait so how do i determine how the plane looks after changing i and j?
you just
drag the grid lines
along with i and j
so that they remain straight and parallel
he animates it in the video like once every 5 seconds lol
thats how its done
i see how its done but i dont get why its turned to that specific angle thou
because the i and j vectors get put into a weird angle with each other
the grid lines need to line up with i and j
so they necessarily follow the same angles
thats before the transformation
probably
after the transformation its gonna get wonky
yeah
no no
thats not the transformation
v is given by -1i + 2j
thats just the definition of v
the transformation is the thing thats sending i and j to where you see they are on the picture
thats the transformation
but why is the i and j that way
like why is i suddenly facing the southeast
wont it face the south
this matrix once youve written it down defines a linear transformation
its effect is moving i and j like you see in the picture
its not that i and j always move that way or something
its determined by the matrix you are working with
i gets sent to the first column
[1 3]
wait its [1 2]
wait sorry how did u get this lol
-1(1,0) + 2 (0,1)
so the first column is [1 -2]
thats where i goes
the second column is [3 0]
thats where j goes
you have no say about what angle theyre at or how long they are or anything
once the matrix has been written down
everything is decided
and i can "sum" up these two
to get the final vector?
the yellow line here
so v = -1i + 2j right
yes
the transformed v
Tv
is just the sum of the transformed i and the transformed j
Ti and Tj
with the same "amount" of each
thats what it means to be linear
we know what Ti and Tj are
thats just the columns of our matrix
aka where i and j are sent by the matrix
so we can calculate Tv as the sum of those
with the correct amount of each ofc
okay i get this part
i still dont get why the plane transform that way lol
like i get the matrix and why when they add up theyll be some new vector on the plane
and stuff
but i still dont see how this relates to changing the entire plane
we could do all these without changing the plane
i think
the thing is that you can visualise the transformation as changing the entire plane
like
the transformation sends the standard cartesian plane
to the new changed plane
this would be without transforming the plane
the fact that the grid lines are still parallel and straight and stuff is because each vector is able to be written in terms of i and j
well yes
you can calculate individual vectors and stuff
but the point is like
you want to have the big picture
or like u said we could also change the plane aka linear transformation to get the resulting vector?
what does this linear transformation do to the whole plane
you usually dont care about single vectors
umm from the video is like rotating it 80 degreees to the right or something
well i mean that just depends on what matrix you write down
theres infinitely many linear transformations to choose from
the video just has a lot of examples
they arent anything special in particular
how does (-1, 2) tell us to rotate right
where does -1 2 come from
the rotation is associated with the matrix
not the vector
you dont care about what happens to individual vectors
you care about how the matrix acts on everything
in order to see how a linear transformation behaves
you care about its behaviour on the entire plane
okay so ill ignore individual vectors entirely
can u tag the matrix that represents this plane again pls
this is a reflection in the y axis + scaling the y axis by 2
okay then the second column from the transformed j
okay so we end up with this
how does this matrix
determine how the linear transformation work
it tells you that i gets set to (-1, 0)
and j gets sent to (0, 2)
every vector is a combination of i and j
so we know where every vector gets sent
because we just need to write out how much i it has and how much j it has
then recombine it after the transformation
in other words
you just drag all the gridlines along with i and j
and that tells you the entire behaviour of the transformation
this is really just saying how many gridlines in each direction the vector crosses
wait "drag all the gridlines along with i and j"
which is why we're talking about gridlines
like say here
all those red lines that ive drawn
thats determined by the fact that i has been sent to (1, -2)
so all those red lines must line up
be parallel
and have the same length
because it forms a grid
same thing for j
i and j completely determine the gridlines
wait could i turn it another way tho
like can the red line here
well ofc
ok wait wut
it depends on the matrix you start with
this matrix fixes those gridlines
another matrix might fix different gridlines
like in the same example, can the red be facing directly downwards (without changing the matrix)
no
the gridlines are completely determined by where i and j go
they must be parallel to i and j
and be equally spaced according to the lengths of i and j
i get that the gridlines must strictly follow i an dj
you see that yellow parallelogram
ye
thats the parallelogram spanned by i and j
the entire grid is that parallelogram
every single cell of the grid is a copy of that parallelogram
you cant form the grid in any other way
thats how linear transformations work
how did they form that parallelogram in the first place tho
its determined by i and j
you know where i and j are
take any two arrows
and you can form a parallelogram with them
sorry but like i get that it depends on i and j
but i dont get why i points in this particular direction
like why southeast
because i = (1, -2)
in this particular case
thats just
what the transformation is
its been decided that i = (1, -2)
so thats where it goes
you cant just be like oh but its actually (0, -2)
WAIT IM STARTING TO SEE IT
great
OHHHHHHHHHHHHHHHHHHHHHHHHHH
THIS
this solved it
AAAAAAAAAAAAA
this is amazing
bruh
good



im off
👋
.close
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Can someone pls explain this step to me
I get there factoring out an x but why is there a positive 1
Because 1 • -2
@vagrant moat @surreal mesa @grizzled raptor @static tree
@ember onyx stop posting in other people's help channels
A discussion about: The distance vs. time when the carts are moving in uniform motion (first experiment) and uniformly accelerated motion (second experiment) using a data table, and the meaning of the slope in the graph velocity vs. time.
@surreal mesa
Is that factoring
@surreal mesa
STOP @ember onyx
where do i post then
I pinged you into the 384 chat
ty
I think it’s because you factor out an X it becomes (x^2-x-2)
Then you do the funny factoring
Isn’t it -x^2-2 when factored
If you reverse it and multiply (x+1)(x-2)
You should get that
Well you’re taking an x from x^3-x^2-2x
They skipped the part where it’s x(x^2-x-2)
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from the first to second line, what is that property called
nyani
taking 2^(blah) of both sides
u can just do that
