#help-39
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can $< \emptyset, 1>$ be an element of the group?
Ayanokoji
Please don't occupy multiple help channels.
or set
Please only have one question open at a time
Do you want to close your previous channel, to ask this new question?
I switched questions and this is pretty small (1m or 1 liner)
Yes, that is an element of R
I mean I can
how's it the condition at the end work then? for any condition I mean
I think the word you're looking for is "relation", not "group"
oh it is, mb
It's vacuously satisfied. It says "check through all the elements of A and make sure they are less than or equal to n"
Since there are no elements of A to check (because A is empty), we are done
great, ty mate I understand now
No problem
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if I have an odd number n, will n+2 always be odd?
yes
yes
great ty guys
the proof for that is really simple too, an odd number is any number of the form 2p + 1 where p is an integer, so let n = 2p + 1, then n+2 = 2p + 1 + 2 = 2(p+1) + 1 = 2q + 1 where q is an integer
therefore n+2 is odd
As in trigonometry, if we get an odd nπ/2 and and even nπ/2 how to determine which quadrant to choose?
yeah that's a great proof ty I needed to see this
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can $<\emptyset,\emptyset>$ be an element of R?
Ayanokoji
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If the solution of the differential equation $$\frac{dy}{dx} + e^x(x^2 - 2)y = (x^2 - 2x) (x^2 - 2)e^{2x}$$ satisfies $y(0) = 0$, then the value of $y(2)$ is?
♥•♥•♥•♥
did you get stuck figuring out $\int e^x(x^2-2)\dd{x}$?
mtt
why?
differenciation of $x^2 - 2x = 2x - 2$
♥•♥•♥•♥
then i can use by parts to solve the integral
so this edited post still has a typo youre saying?
♥•♥•♥•♥
that's better :D
so what part are you stuck on
yes
you see that exponent in e^((x^2 - 2x)e^x)?
it would be nice if that exponent was just u
so let u = (x^2 - 2x) e^x
then from there, figure out how to write the rest of the integral in terms of u and u'
part of it involves splitting e^(2x) into e^x * e^x
@brisk marsh Has your question been resolved?
@brisk marsh are you still stuck
yeah
are you stuck on the integral
you only need the integral from 0 to 2, since you know I(0) = 0
that doesnt work out when I tried it
the (x^2 - 2x) term on the left prevents any info about y(2) from getting out
@brisk marsh hello?
@brisk marsh Has your question been resolved?
irrc its supposed to be e^((x^2-2x)e^x)?
the integral?
we already covered the integration factor to get here, what is your point?
Catted
Compile Error! Click the
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(You may edit your message to recompile.)
why are you calling that an integration factor?
the integration factor then is $\mu(x)=e^{\int p(x)\dd{x}}=e^{(x^2-2x)e^x}$
mtt
yes but here you wrote it as $(x^2-2x)e^x$?
Catted
oh tahts a typo, I completely glossed over the missing e^
I really need to take your hints next time
i think the guy already got it
@brisk marsh did you already figure this out
no i went to watch yt instead of solving it 😭
bruh
I pinged you a few times
anyways there was a typo in the image before
this should be the correct version
did you do the u-sub yet?
I already said that
oh
thats correct
why not just evaluate the integral from 0 to 2 now
wait lemme catch up
they need to take their time
@brisk marsh also are you allowed calculators
dont i need to solve the definite integration first
i mean indefinite
$e^{(x^2-2x)e^x}y=\int_{0}^{x} (x^2-2x)(x^2-2)e^{2x}e^{(x^2-2x)e^x} ,dx$
Catted
what
plug in 2 to get $y(2)=\int_{0}^{2} (x^2-2x)(x^2-2)e^{2x}e^{(x^2-2x)e^x} ,dx$
Catted
wait how did u get the limits
isnt is supposed to be indefinite integration
then i get the value of integration constant by putting y(0) = 0
@brisk marsh so did you do the u-sub yet?
do you remember what I told you?
about the exponent?
this is your integral
it would be nice if that long exponent in the integral was just a u
so I suggest that you do u = (x^2 - 2x) e^x
@brisk marsh so go u-sub u = (x^2 - 2x) e^x
if i put $ t = (x^2 - 2x)e^x$
then $\frac{dt}{dx} = e^x(x^2 - 2x) + e^x(2x - 2)$
oh
also you can do \dv{t}{x}
♥•♥•♥•♥
to get $\dv{t}{x}$
mtt
its shorter to type
cool
now simplify dt/dx for me please
$\dv{t}{x} = e^x(x^2 - 2)$
♥•♥•♥•♥
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✅
ayo dont close the channel just like tht
i just got the answer lemme thank all these ppl
THANK YOU SOO MUCH!
if you watch youtube then theres a good chance you can forget anything
I can attest to that
lol
i am just not in the mood to do em
so i am half heartedly doin em
maybe i just just commit to watchin yt and do em later
or you can commit to finishing this now
so that when you commit to watching yt, you have no time pressure
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Kacka found a number n that has k divisors (including 1 and n itself). She took all these divisors, sorted them in ascending order, and numbered them as 1 = d1 < d2 < … < dk-1 < dk = n. She found that the following equation holds:
377 * d2 + dk-1 = n
Find n.
I have no idea how can i solve this
@ivory hornet Has your question been resolved?
d_2 and d_(k-1) will be factor pairs and multiply to n
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how do i do this question
,rotate
.
why did you just split it at the start
surely you know the integrals of csc^2(x) and sec^2(x)
oh yeahs
forgot about that
but how do i use the integrals of them in the question
∫[(sec^2(x)*cosec^2(x)][3+sin^2(x)] dx
is what im getting
How r u getting this its not correct
oh wait
When u distribute the denominators u should be getting integral of 3cosec^2(x) + 4sec^2(x)
edited
wdym distribute the denominators
I mean like if its written (5+6)/2 u can write 5/2 + 6/2
right yeahs
Similarly u do this and cos and sin will cancel out
yeah so i got 12∫dx/(sin2x)^2 + tan(x)
dunno what to do with that integral though
@raven spade Has your question been resolved?
@raven spade Has your question been resolved?
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hi! just wondering if anyone could please help me with this question. i've already got 1a, which is 1+5x+10x^2+10x^3+5x^4+x^5
.
u first want to find the ratio between each term
yes!
it's -1 right? but idk how that impacts (1+x)^-1
so -x?
would it be ok if i use the binomial theorem formula? would it still work if the power is negative though?
remember that this is a series
oh, so would this then be the sum of geometric series? finite
<@&268886789983436800>
hmm this finite stuff is throwing me off
hmm is it in reference to this series
i'm not actually sure whether to use sum of finite or infinite geometric sequence - i didn't really understand the first line of 1b to be honest, i just took finite from the question.. but technically there should be infinite terms in the power series they've given, right? this is what i'm referencing right now
right
that first line also throws me off
i think it should be an infinite series
assuming that its an infinite series, what would be its sum?
let me send you a picture of my working out right now
i've proven it's (1+x)^-1 i think, but i'm not sure what it means by state the values of x for which the equality is true. wouldn't it be all real numbers, because x can be anything?
not necessarily
note that our ratio, r, must have a magnitute less than 1
since the sum of an infinite series only converges (doesnt go to infinity) if it's ratio has a magnitute of less than 1
ohh, i see!! so -1<-x<1? as the ratio is -x
correct
so it would be like 1>x>-1 if we convert the negative to a positive sign
yes
ohh i got you thank you so much!! i haven't really looked at 1c so i'll have a look considering the steps for 1b. thank you again :))
all good
Hi, so sorry to bother you again! I just finished c and d but I’m unsure how to solve for e. There seems like there would be 2 options for either an odd or even power — as in, if the power was odd, the sequence would start with a negative one, whereas it would start with positive 1 if the power was even
right
so its good that u noticed it alternates starting positive and negative
do u notice anything about the coefficients of each term?
all coefficients seem to be alternating positive and negative? the power of 3 seems like they're triangular numbers and the power of 2 is just consecutive numbers
wait
i think u made a slight mistake with the 2nd derivative
ur 3rd sequence should also start with a positive
these are different
OH you're so right, i think i copied the wrong sequence, let me fix that real quick
yes thats correct, but there is a specific place that they come from
pascal's triangle?? could i then use combination to calculate the coefficients?
the diagonals? i am trying to figure out how to represent these using combination
yes
it may be easier to work with the diagonals going from top right to bottom left
since the series of 1's are all the first number of each row, and the 1,2,3,4 series are all the 2nd number of each row, and the 1,3,6,10, series are all the 3rd numbers of each row.
something like that? i'm unsure if the lower number would be 1, but i'm guessing the top number has to increase by 1 with every variable
hmm u have the right concept
but the top number represents the row
and the bottom number represents the position in the row
Nice handwriting my guy
it may be easier to focus on just the series of 1's then build on from there
so 1 would be like the last number in each row, and then the position decreases by 1 with each further term? does this make sense 😭
the series of 1's are just the first number of each row, but remember that pascals triangle starts from 0, so they are technically the 0th number of each row, and note that we just have to increase the row number each team so it would be 0C0,0C1,0C2,0C3,etc
i think ur getting ur directions mixed up, pascals triangle reads from left to right
so 0 is the row number for every term in the sequence? sorry i am a bit confused :((
0 is the position in each row
remember that a row goes from left to right
so each row goes like
1
1,1
1,2,1
1,3,3,1
1,4,6,4,1
1,5,10,10,5,1
notice that the 1 is always the first number of each row
but like i said, in pascals triangle we start from 0, so they are the 0th number of each row
yes, but 1 is only the first term of the sequence, right? the next term would move to the next row, with the second term and thus the 1st number in a combination representation --
correct
now lets take a look at (1+x)^-2, ignoring negatives for the moment, the coffecients are 1,2,3,4,5,6,7,... etc right
yes
correct
like wise for (1+x)^-3 all bottom numbers would be 2
can u notice a correlation between the power and the bottom number?
bottom number is 1 less than the power?
correct
yeah that looks fine i think
yes
ohh okay thank you so much for the help!! i'll have another look at this to consolidate my understanding 💙
@lavish flax Has your question been resolved?
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How do you use stoke's theorem on a cylinder-like surface?
@unborn cosmos Stoke's theorem can only be applied on surfaces with no holes in them. In order to get the area of the surface with a hole you can apply Stoke's theorem twice and subtract.
Imagine a fully connected surface, bounded only by C2, then consider just the hole bounded by C1. If we find the integral of C2 to be I and C1 to be J, wouldn't it stand to reason that the integral of the surface with the hole in it is I - J?
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where is the "hole" coming from>
@unborn cosmos the surface has a hole through it, topologically
yeah that's what i thought
hmmm
why I-J?
gahh
i'm getting confused with the orientations
and which one is negative
Clockwise is negative
anwyays
so the basic idea behind this is that
topologically, this is equivalent to consider a disc with a hole in it
outer boundary = C2
inner boundary = C1
Yup
for the line integral or the surface integrael?
oh wait
The line integral, right hand rule to the normal vector of the surface
and so for the "hole", I just pretend that it wasn't a hole
Yup
and compute the line integral on that
Exactly
Exactly
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what do you need help with here??
Dis
I'll try
Thx
np
Which is?
use calculator if you're stuck on simple questions
But idk how to put equations
21 * 21 * pi = 441 * pi = 1385.44236
O_o
but be careful what the question wants
My mind is mush now
Is that the answer?
It's 1dp
ok so you tell me what should it do
I don't see clearly
The radius of the circle below is 21mm
Calculate the area of the circle
What?
that it's 21mm not cm
What's the dif?
you have to convert the units
O
I gave you the answer in cm
Want ste answer in mm2
that's the answer in mm
?
yeah I think that would be the answer
It's wrong it says
hmmm
?
let me think
Ok
.4
Huh?
1385.4
Yess
you round it wrong
Mb
when you round something be careful
same work
7.3 * 7.3 * pi
in 1.d.p
if the 2nd.d.p = 5 or more , you add 1 to the first d.p
What's the answer cuz I don't understand *
Idk
If you feel tired or something go rest or sleep maybe
Nah I need to do this first
It's due tmr
My hw
ok so you need to focus
I can give you the answers
but you need to understand the questions
Yes plz
Ok
7.3
I still don't understand
what's the area ?
Prob 7.3cm
Ugghhhhh I need a shower still I get dis shi
to find the area we have to know what is the law of the area of the circle
Welp idk
I will go now , try to focus more and you'll get everything
Can u get another helper?
<@&286206848099549185>
So, what is the question?
?
Don't you know how to calculate the circle area?
You don't know the formula, or don't understand the formula?
Both
Can u give me the straight answers?
?
Plz
I have to calculate this?
.
What's the ^
Not working
Why?
Idk
I'm doing what ur saying
So
Write me this number
You got
It says syntax error on my calculatr
Why?
Should I skip this part
I don't know, can you use another calculator?
Nope this my only one
Phone?
Idk how to use phone calc
Ok....
Ima skip this
167.41547250980
That's the answer I got, but you must know how to use phone calculator
That's right
That's hw answer
Sorry, for my bad english
Translate please
Thank you so much^
Ok
Tysm means Thank You So Much
Thanks
What's this
Nw means No Worry
So, you should use the same formula
πr^2
π multiplies by 16.9 and multiplies by 16.9 again
@mint tiger Has your question been resolved?
So do you have more questions?
If you need, you can write to me later
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I’m not sure if I solved this right… or the right way to solve this. Can anyone help?
when you do f(x+h), replace the x with x+h
you just did f(x) +h
5/ (x+h)
with the whole x+h in the denominator
lmao fair the brackets are off but we get what they mean
LMAO im actually so bad at functions
without them its exactly the same as what they did
and that misinterpretation is what lead to the error
tru
$\frac{5}{x+h}$ btw
Skill_Issue
ok i rewrote it at the bottom
now is the next step to find the LCD of all the values in the numerator?
remove the h
still incorrect
really?
yea :(
if its
f(x+h)
and f(x) = 5/x
wouldnt i just plug in 5/x where the X is?
why would i remove the h
plug in x+h where the x is
you remove the extra +h you have
isnt it what i wrote above without the h in the denominator?
uhhh
lets break this down
yes please 😭
youre subbing in x+h where the x is right?
correct
just an example
?
f(x)=5/x?
yes
or we just doing an example
ok
heres the thing
i think you might have the f(x) mixed up
whatever the f(x here) is, we sub into the x of the equation
is it possible to get into a call with u and explain with voice by chance
if not thats ok just thought id ask
nah sprry
ok
np
ok that makes sense
in the f(2)
u replaced x with 2
so u put 2 wherever x is
yep
yep exactly
then if you have f(x) = 5/x
and were trying to do f(x+h)
wed sub the x+h into where the x is
can you try write that
i thought that if f(x) = 5/x and we are trying to solve f(x+h)
we'd just put 5/x where the X is
so f(5/x + h)
thats wrong?
is wrong
yea thats wrong
you put x+h where x was
its the same thing as this
just instead of f(2), its f(x+h)
to get f("whatever that is")
replace all x initially present with "whatever that is"
there needs to be an x in the equation
there doesn't
so ill give you f(x)= x^2
ok
if you want to find f(x+h), what would you do
f(x) = x^2 / f(x+h)
so like i did before, if i didnt know better. id do
f(x^2 + h)
but ik thats wrong
so what do i do instead?
yep
so the x is being squared
then we want to replace the x with whatever is inside the f()
we see that its f(x+h) so w replace the x with (x+h)
so would it be (x+h)^2
how do you know which function to sub into which
cause apparently theres 2
f(x) = x^2
and f(x + h)
how do know which goes into which
thats the main function
this is a translation of the main function
so we will sub it into the the f(x)
so the translation always goes back into the main function?
uhhh
its more like
finding a point
on the function
nah thats wrong
cant explain it clearly lmao
yep
the formula is made up of parts
there are parts f(x+h) and f(x)
so we need to find both these parts and subtract
okay
i see
i just always thought you put the function into the formula..
main function
ok so in this case
I do
lemme send a pic
like this
i can send a pic
yep exactly
ah.. ok
ok
would the next step be
multiplying the numerators
by each other
so (5/x+h) * x
(5/x) * (x+h)
so they have a common denominator?
remember when writing these you need to put brackets around the whole denominator
so 5/(x+h)
the x is stand alone
so you know its just x on the denominator
yep will do itll be quick
i can look over it to see if theres anything wrong
yep
ok
so in the end
id get
(5h/x^2+hx) <--numerator
/ h
is that correct?
its the same as the last part of my work above but 5h instead of h
lmao even inside the numerator 5h/(x^2+hx) but yep youre on the right track
ah ok
and then i used the formula thing
(a/b) / c
=
a / (bc)
so heres my new answer
you added not times
dont open the brackets btw
so just do
5h <--- numerator
(x^2+hx) (h) <--- denominator
is that right?
O did you leave @sterile turtle
sorry
yea
thats right
ams if you see
You have 5h/(h(x^2+xh))
so why not cross out the h
Do I distribute the h?
OHHH
I can remove 1 from the top
So 4h / (x^2 + xh)
Right
?
yea
So 5 / (x^2 + xh)
👍
I took pre calculus 7 years ago
In high school
And then
I didn’t take much math since
ahhhh
fair enough lmaoooo
nah good on you mate
And would that be the final answer since we can’t simplify anymore
yep
Thank you sir ❤️
npnp
Wait lemme put it in answer
To test if it works
Need to load up my pc one sec
It says that it was wrong @sterile turtle
So it’s just -5 in the numerator right? And same denominator
aight im not gonna be able to help anymore so gl
yep
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do you want to know how to find such a factorization
or do you just wanna know why they're equal?
MATERIALS:
1 This is a relational quadratic function) that, when graphed, can show input vs output growth.
2 As with all functions, I'd imagine you could just plug in a value and check the result.' Why is it they'd want to factor the answer if they logically should be able to just plug in a few values to find what the operations would come out to?```
CORE CONCEPTS (that I''m aware of):
relational graphing x,y difference
factorization: breaking numbers down into parts that multiply to make a whole
algebraic factoring: reforming problems into quantities or a n y form that, so long as it multiplies to get the whole, is correct.
algebraic operations: attempts to narrow down an answer via various methods, typically involving inverting or manipulating the problem in some way.```
sorry what is your question exactly, are you asking why we care about factoring?
my understanding: Functions are given input and produce output. Why would we need to factor to find what input would create zeroes when we could just input values to figure that out?```
i mean good luck finding 5/2 and -1/3 without factoring (or some other technique using the polynomial itself)
you won't find it by guessing and checking, unless you're using the rational root theorem (which I'm 90% sure you don't know)
FAULT: Did not use if & if not operator reasoning to check for usage.
UNDERSTANDING: You are saying that they simply use it because they can't any other way? It is more complex than it appears?```
Q: You mean fractions or whole numbers of the form 5 and 2?```
i mean that the solutions to these quadratic equations won't be integers in general
it just makes you less likely to find it, unless you pick an enumeration of the rationals and then start checking, which is EXTREMELY inefficient
also, what is FAULT? is that for you or for me?
me
got it
but yes, it is more complex than it appears, and you have to learn how to factor becuase it's an easy-to-understand version of the "real" technique for finding zeroes of polynomials (without relying on the quadratic formula)
which generalizes to higher-degree polynomials
and is computationally more efficient
Q: How is it that factoring the polynomial ends up producing the roots?
simplified: How does breaking a problem into smaller pieces and finding the values you could break it into that would negate all values generate the zeroes for X?```
no need to ask the simplified question, the original is coherent (unless the simplified version is again for you)
It mostly is, as I was attempting to word it in such a way that the answer would be more attainable. It may also make my thought process more visible.
but we factor a polynomial so that we can use a particular fact about real numbers, namely that if ab = 0, then either a = 0 or b = 0, and also a fact about polynomials, namely that linear maps have exactly one value of x such that f(x) = 0, and if you take a product of nonzero numbers, the whole result is also nonzero
so if i have like, x^2 - 1, then it's a quadratic, and these facts don't say anything about quadratics, but if i factor this polynomial into (x + 1) (x - 1) , then i can use the fact that f(x) is 0 if and only if x is either 1 or -1 by the two facts above
this is why we try to factor stuff first, because it's clear now that f(x) and the factored version have the same outputs, but the factored form makes it REALLY CLEAR where the roots are, and that the solutions to the factors can be the ONLY roots
this is if you can factor the polynomial in the first place. But we would like to check for it whenever we can because this theory is very nice
polynomials have such a rich theory just becuase we really like computationally efficient methods for computing their properties (and also because geometrically they're very interesting, but if you're looking for immediate applications in areas of math that are understandable or practical in science, then i think that being computationally efficient as an algorithm is a great place to start)
btw
map generation (games)?
perhaps yes, maybe not for this algorithm specifically, but there is a nice theory of approximation that might be applicable in map generation
I don't know much about game creation
or the cutting-edge when it comes to that
Ok, it's just that someone was using it for that interestingly.
Thank you! I believe I need to deeply think about this for a while.
Gl!
have fun exploring
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how do i turn left to right?
theyre equivalent but idk how to turn it
start by using double angle on sin
sin ( 2theta/2)?
yes
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here am I allowed to use the polar form of a complex number $(re^{ix})$
ƒ(Why am. I here)=I don't Know
I don't think so
You gotta first define it
why would or wouldn’t you, it just depends on if you’ve covered it
This is the first chapter of LADR
For that you have to use these
oh then you can’t
Use the normal definition
i’m assuming that you can’t because axler is terrible and probably didn’t define polar form

god i hate axler
And prove that they are equivalent
if you want to do it the based way, identify a complex number a+ib with the 2x2 matrix [a -b; b a]
then it comes from associativity of matrix multiplication
Lol that's based
thanks
there’s a nice spot the mistake question related to this
this is from a friend who came up with this a few years ago: Everyone knows we can prove matrix multiplication is associative by considering matrix multiplication as a function: let f(x)=Ax, g(x)=Bx, h(x)=Cx, then (AB)C represents (f o g) o h which is f o (g o h) which represents A(BC), so (AB)C = A(BC). We specialize to the case of 1D matrices, plug x=1 into both sides, let the matrices be over octonions, and voila, octonions are associative! Where's the mistake?
you could, in theory, do this question right after learning about how matrix multiplication is in 1-1 correspondence with linear maps
but whatever
👍
it’s just a funny aside
ƒ(Why am. I here)=I don't Know
Like the derivation?
I mean while defining complex numbers
If so yes
because this is rather painful without euler's form
offhand i'm guessing it's because validity of matrix multiplication as the way to calculate compositions depends on the fact that you're in a vector space over a field, or at least a module over a commutative ring?
yes thats the key, but you don’t need the ring to be commutative, just associative (for matrix mult to be composition)
yes, and good job
Yes
ah nice
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i get no answer
Oh yeah
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Let $A$ and $B$ be $n \times n$ matrices. AB=BA. Given that $\xi_1, \cdots, \xi_{r_1}$ and $\eta_1, \cdots, \eta_{r_2}$ are the fundamental solutions of the systems $Ax = 0$ and $Bx = 0$, respectively, and for the $n \times n$ matrices $C$ and $D$, it holds that $r(CA + DB) = n$.
How can I prove that $\xi_1, \cdots, \xi_{r_1}, \eta_1, \cdots, \eta_{r_2}$ is a fundamental solution set of the system $ABx = 0$ ?
nino
@agile ridge Has your question been resolved?
Can i ping <@&286206848099549185>
I saw that you edited, n-rank is very different from 'n x n matrices'
Translation error, sry
ok
