#help-13
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Imma trying to conclude my understanding in these drawing...
Anything wrong?
Its about set by the way
You didn't label A and B in the second one.
If they're the smaller two, then it's the combination of the circles, not including anything outside the circles.
Ogey
Anything wrong again?
Yes. You've labelled the union as some elements outside of A and outside of B.
union set is surely wrong
Ogey (????)
It needs to be like this
The union doesn't include anything outside of A or B, so you probably shouldn't label the section that includes things outside A or B as the union.
No, that's also wrong.
also name what you're trying to show- the belongs to
it's correct
You're labelling lots of elements that aren't inside A or inside B as being in the union.
when did i label
that's a way of showing it
The square contains lots of elements not in A and not in B.
yes
That's why it's wrong.
You're labelling the universe as the union, when it's not.
Ill sit for a while trying to understand what is not my native language
You said A U B underneath a square, meaning that the square is A U B.
The square isn't A U B.
bruh
we r clearly speaking about set a and b
so a U b makes sense
I have no idea what you're talking about.
A U B doesn't mean something that also includes A U B. It means something limited to exactly A U B.
You can't just draw two unshaded overlapping circles and then write A U B near it. You need to shade or properly indicate which part is A U B
You didn't limit it in any way to exactly A U B.
yes
You merely labelled a rectangle as A U B, when that rectangle includes more than A U B.
fine but I was just showing him u need to intersect the sets
Okay...
So like...
U make a first circle...
Then it filled with 2 circle only "a and b"
So the first circle called union?
The union is the combination of all elements in A and in B.
If it's in A, it's in the union. If it's in B, it's in the union.
So we cant draw it with circle???
If they're separated, there's just no elements in the overlapping part.
They should be drawn overlapping to be more general.
Overlapping doesn't mean the overlapping part contains any elements.
But if you draw them apart, you're not handling situations where they both contain the same element.
So overlapping them to make it look more "united"?
No, it's to work for all sets.
seeing a face
The sets that don't contain any common elements will merely have nothing in the overlapping part.
So, it can handle all situations.
if it doesnt overlap then A & B is the empty set
But if you don't overlap them, you're not covering the situation where they contain any common elements.
we make it overlap to make it more general
because most cases two events have an intersection
We're talking about unions.
Ik
That's why unions are drawn like here: https://en.wikipedia.org/wiki/Union_(set_theory).
If you're trying to handle all possible sets.
If you're drawing it for two particular sets, you can do otherwise.

Learning math
Ogey...
Im starting to understand
Btw thank you very much ! @kindred storm @fervent jackal @mild sundial
I hope we meet again!
No problem.
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looks like a trig substitution problem
wait heres a better picture
but yea...idk how to do that
u := arccos(x) suggests itself
...what that mean cuzzo
the substitution u := arccos(x)
yea ion think im that ahead bro
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(do you know what a u-substitution is?)
i missed that class
prolly should learn that or can yall jus help
ill learn after too
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Stuck in the first one I'll translate it
A, B, C and D are points on the circle
AB and CD meet together at point F.
<DAC=<DBC
<ACD=<BCD
Prove that DC is a diameter (already did)
Prove that AB is vertical to CD
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,
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I have 8 coins, and I will pick 2 of them and add their values up. What can I set the denominations of the coins to be so I can get the most consecutive values starting from 0? (With one of coins being 1, and another coin being 0)
I know the maximum I could theoretically get would be 36 or (8 * (8 + 1)) / 2. I solved it through a brute force search and got 0,1,2,5,8,11,12,13; which can cover every value from 0 to 26. How can I solve it without checking all 2 billion combinations?
0,1,2,3,4,5,6,7 can do 0-14
0,1,2,5,7,10,11,12 can do 0-24, which was the best I could come up with by guessing
i'm a little confused by your description of the problem, because assuming you can't pick up the same coin multiple times 0, 1, 2, 5, ... , 12 cant do 4
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You can pick up the same coin both times*
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Hi, is there any way to obtain 3x3 matrix that have 3 eigenvalues (1, 2, 3) and has 7 non zero elements?
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Yes, there is!
Hint: You can choose A_12=A_13 = 0 and A_11 = 1
I tried something simmilar but I am always stuck with a case that determinant is -1
basically I do not know what to put in other places
Ok, do you know what the advantage of this choice is?
no I do not
If we want to calculate the Ev we need det(A-x*1)
Since there is only one non 0 entry in first row we can apply Laplace
Ok?
ok we have something like a polynom that needs to be zero
in order to get zero as determinant and have eigenspaces when working out kernell
but well I do not know what you mean by Laplace
Laplace method to calculate the determinant?
If there is only one non 0 entry in a row the determinant can be easily calculated
Never heard of that?
Ok, no problem. I don't have a lot of time explaining the method to you though
Oh I see I believe Laplac is when you choose a line or column and you could calculate detminant as sum of sub determinants
am I right>
?
Exactly
we just call it differently
Doesn't work
Ok, since I am a bit in a hurry: If you applied Laplace for Det(A-x1) for the given entries you would get (1-x)โข some polynomial
Ok, sorry that I couldn't explain in more detail. Good luck
Now there are only 4 entries to worry about
ok I belive I will manage
do not worry you were helpfull
You will for sure ๐
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Where am I wrong
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@glossy sigil Has your question been resolved?
Have you subbed in the initial conditions
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@glossy sigil Where in your equations do you use 1.1million?
so then what did you get for c?
Normally you would expand "e^(.05t + c)" to "e^c * e^.05t"
then you can just use a different constant: y= Ce^.05t + 1million
that way solving for C is easier when you plug in your initial population: 1.1million = Ce^(.05*0)+1million
(since e^0=1)
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Hello
Does anyone know the second symbol name?
lambda, sigma, rho
Lowercase sigma?
lowercase yeah
Uppercase is the summation symbol
it's also very frequently used to represent a permutation
or in probabilities for the variance or standard deviation (std I think, not sure though)
variance is sigma^2
yeah that's what I thought
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how does this work?
is it just divided by log?
no
"dividing by log" is an error so serious it's a real DROP EVERYTHING, THIS IS AN EMERGENCY situation
log(x) isn't the product of x with something called "log"
log is a function and not a number!
10^LHS=10^RHS
and here specifically,
log(x) = 0 => x = 1
or that, assuming the log is implied as log_10
Unless log refers to log base e
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doorslam!
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I don't understand this. why is W a subspace of Rn?
which step confuses you?
W is a set containing vectors of an equal amount to the dimension of R. each a is a coefficient of each vector. if if there are some a(s) that let you set all the vectors to 0, its a subspace?
whats the "for all i, 1 <= i <= m" part for?
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i think you misunderstand...
ok so like
you have here essentially a system of linear equations
a homogeneous one at that
the statement is that its solution set is a subspace of R^n
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why is the hessian the jacobian of the gradient, rather than the jacobian of the jacobian? i know that the jacobian is the generalization of the derivative for functions R^n to R^m, but for multivariate functions R^n to R^1 for some reason we use the gradient instead (the transpose of the jacobian). i am confused generally about why this transpose is necessary.
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let rotation be defined as this
how can i write this rotation in a form of matrix?
(e_1,...,e_n) is standart basis
I'm not clear on the rotation that's happening here
Oh wait, where we let e2 be fixed?
We find the matrix for any transformation the same way:
- Plug the basis members into it
- The results we get form the columns of the matrix
what do you mean?
can it be like this? @upper abyss
in each column i wrote mapping of that basis
yes it is correct
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how do i solve this to the x1+x2+x3-b=0 form? (the topic is vectors)
is it 3x1-x2+x3-5=0 ?
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sofficino9188
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...
l.65 so $c+(1/n)โ
A$, which is absurd because $c$ is the largest of all the...
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Prove that if $A$ is a regular matrix, then $A^T$ is also a regular matrix, and its inverse matrix $(A^T)^{-1}$ is equal to the transpose of the inverse of $A$, i.e., $(A^{-1})^T$, where $A^{-1}$ is the inverse matrix of $A$.
Slowaq
this isnt sufficient is it?
i did not show that A^T is regular matrix
how should i do that?
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How do you solve this?
mhm?
That's just the definition of e
It's just the limit definition of e
In general :
how do i prove it
idk how to prove it, sorry
Check out the blog to follow the series! https://centerofmathematics.blogspot.com/2017/08/episode-9-limit-definition-of-e.html
i don't think u have to prove it
by definition, e is equal to that limit
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Can somebody help me find the time complexity of this Dijkstra algorithm implementation in python?
def dijkstra(graph, start):
previous = {v: None for v in graph.adjacency_list.keys()}
visited = {v: False for v in graph.adjacency_list.keys()}
distances = {v: float("inf") for v in graph.adjacency_list.keys()}
distances[start] = 0
pq = PriorityQueue()
pq.add_task(0, start)
while pq:
removed_distance, removed = pq.pop_task()
visited[removed] = True
for edge in graph.adjacency_list[removed]:
if visited[edge.node]:
continue
new_distance = removed_distance + edge.distance
if new_distance < distances[edge.node]:
distances[edge.node] = new_distance
previous[edge.node] = removed
pq.add_task(new_distance, edge.node)
previous_str = {str(k): str(v) for k, v in previous.items()}
visited_str = {str(k): v for k, v in visited.items()}
distances_str = {str(k): v for k, v in distances.items()}
print("Previous:", previous_str)
print("Visited:", visited_str)
print("Distances:", distances_str)
return
@primal stag Has your question been resolved?
#old-network for CS server
Or find a python server
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(-i)^2 = -1
but
(-1)^2 = 1
how is this broken down please? because idk if I am right here, I deduced this for the 2nd equality: (-i)^2 = (-1^2) * (I^2) = 1 * -1 = -1 is this right?
i is the sqrt of -1
So when it's squared the sqrt is cancelled out
(-1) squared is 1 because the negatives cancel out
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Interesting question
do you have any idea of how to start it off?
(did you try the hint they gave you?)
i tried replacing Q^T and Q from the hing with the given equality for Q
but I only got the transpose part to I + vv^T alpha
so it's still not the same as Q
yeah, i just realized that
i am trying to expand Q^TQ now
any ideas how to simplify this?
i got it
thanks
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R = {(n,|n| + 2) : n is an element of Z} is a subset of Z x N
I understand this as a relation. What im having trouble with is understanding is how a function can go from Z -> N
Z being set of intergers and N set of natural numbers
Do you mean overall how can there be a function f: Z -> N
Well, I know in the set it mentions n can be integers and when you plug in an integer to |n| it will be a natural number
its just odd that after the set they mention is a subset of ZxN
could you still write that if y = n + 2 instead?
I mean this is not because through this relation every element from Z relates to some element from N
not odd*
true
but if n is an element of Z why not just write its a subset of ZxZ?
because regardless, if you enter an interger for |n|+ 2 youre going to get a natural number
well yes, you could write as well f: Z -> Z and it would be ok because Z contains N
its just.. if we know that every value that the function can have is positive then we would as well denote it as f: Z->N
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I have done A but need B
Derivative equal to 0, study intervals between critical points
Yes, but you don't need it
Dp/dt = -4.1sin(PIt/2.3)
Dp/dt = -4.1Pi/2.3 cos(Pit/2.3) ?
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How do you find the inverse derivative of this function at a?
Use inverse function theorem
yeah I know that
but you need the value of f^-1(2) in order to use inverse function theorem
so I know I could set
2 = x^3 + 3sinx + 2cosx
but from here idk how to solve this
plug in easy values for x
oh like 0 or something
wait
no fucking way
I accidentally found the answer
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Hi, I am optimising the above with Lagrange but didn't get n in the system of equations. How do I solve then?
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You're missing equations in the gradient
you only took partial with respect to m. you also need to for n
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ignore the pictures of work but i am pretty confused with how to approach this problem.
not sure if we need to use 2d forces in this or projectile motion kinematics
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the second vector having zero as its third component lets you rule out a bunch of the options
like, the first vector [1,1,1] would require having -1 copies of u, and the first two components obviously can't be reached using v
also one of the options is in a very similar form to your given vectors
yeah
kk ty, one more thing tho
this might depend on your textbook
but zero vector should be parallel to everything
if you define parallel vectors to be vectors with the same span
then they aren't
but that's rare
last one as well
well
actually, if "same direction" means parallel
then yes
if you have an alternative definition that may be wrong
that's why I'm asking
"direction" isn't really a standard term -- it could be different depending on the course
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can anyone help me with this
@azure lagoon Has your question been resolved?
complete the square on the denominator
the result should be an arctan integral or something similar
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how would you parametrize a cylinder x^2 + y^2 = 9 in cylindrical unit vectors?
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Help with this question please
I got u=1-x^2+y^2
And v=-2xy
Is that correct
For part A
<@&286206848099549185>
yes
@flint python Has your question been resolved?
So, the locus of Q when P moves along the line y=4x 16x^2โ8x^2=8x^2
For part b
@valid tendon
<@&286206848099549185>
this looks like it might have been GPT'd.
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so i must select which of steps are invalid in this attempt at showing that the equation has no real number solutions, but they all look right to me... ๐ญ any help appreciated
im pretty confident that 1 and 2 are correct
check step 3 closely
after step 2, we have
(xยณ - xยฒ + 1)(xยฒ + x + 2) = 0
what can we conclude about it?
both things in the parenthesis must equal 0? but i thought thats what they said uhhhhh
think about the solvability of a third degree equation
what is the product of 0 and 2?
0
were both factors 0?
alright
I'm sure that's not how you approach the question
:0
wdym?
a ร b = c
a and b are factors
were both factors here 0?
think about the solvability of a third degree equation
wait where did the 0 and 2 come from?
example
a third degree polynomial always has at least one real solution
i forgor abt that
-.-
you are not helping
yes, you're right
but that doesn't help if the asker cannot use it because step 4 ruins it
so that helps you to think about the given equaiton
OH i seee what u mean
anyway, if 0 ร 2 = 0, do you need both factors to equal 0?
that's it!
okk
step 3 is the offender :D
it only proved that the second factor can't equal to 0
but per this, the first factor can be 0
please find the roots to make sure that 6 is also wrong ;)
yes ok, just only wanted to realize the fact ab cube polynomial ๐
oo okay
we must resolve the actual question before proving that the final step is incorrect
this time, the offenders are step 3 and 6
mhm
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how does the claim get to the last part?
like why did the (n+1) turn into just n for the sequence 0,1,...,n
:0
ohhhhh
i thought the (n+1) turned into n, turns out its the a0+an that did
thanks!
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A pleasure 

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I NEED HELP!
Use the second equation
try making the bases equal
so like, 9^(something) = 9^(something)
do you know how to turn the 3^(10x) into 9^(something)
here is the answer
yea thats fine
what is happeneing in the answer
answer my question though
they made a bunch of subs
okay so like
do you know about the exponent identity $(a^b)^c = a^{b\cd c}$
no but i know now
okay ill write that down
ohhhh
i want you to seperate it into two
so that you can get something that gives u 9
so like
3^(something) = 9
what is something
okay good
why do we need 9
we want our b = 2 here because 3^2
oh for the other side?
5?
agreed?
okay so we get
9^(5x)
NOW the reason we did this is because
there is another exponent identity
[
a^x = a^y \Iff x = y
]
ohhh
if two numbers have the base, and are equal, their exponents are equal
note this down too
science?
yes
teach me
!occupied
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im form 1
so taffy like
[
9^{y-11} = 9^{5x}
]
how does this simplify
wdym?
yes!
so keep this in mind alright?
this is the other equatuoin
yes
equation*
okay
another important identity relating to logarithms, (this is their definition): [
\m{\log_a}{b} = c\Iff b = a^c
]
try doing this here. what do u get
yeah exactly
yay
but remember
we have this as well
so how about you plug in the y here
into y - 11 = 5x
what do uget
you know that y = (x+1)^2
and you have a y in y - 11 = 5x
which you can replace with (x+1)^2
still doesnt make sense?
why are we replacing it
i had logarithm for exam today, it was nice
because the issue is that to solve an equation we need to have one variable in it
!redir
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if i give you an equation with 2 or more variables
you cant "solve" for a variable and get a number
but if you have 1 variable, you can solve for that variable and get a number
you combine them?
y - 11 = 5x has two variables, so we cant get a value for x
yes
(x+1)^2 - 11 = 5x has one variable, so we can get a value for x
does it make sense?
yes
yes
but it has 2
you said it had 1
one variable, which is only x
im not talking about the degree of the variables
it only has one letter-type
if you want me to say it that way
wait what are the 2 equations
y - 11 = 5x
y = (x-1)^2
okay but thats what i am saying we can get rid of the y by substituting the second equation in the first
we can reduce the first equation from having two variables to only having one
okay first of all, the 11 magically got an x and the 5's x vanished
and also, why is 11 negative?
yes
do u see how we reduced our two variables to only 1? thats what you always want to do
if you have two or more equations and you are trying to solve for a variable, try to substitute one of the equations into the other, by solving for one of the variables, thereby reducing the amount of variables
okay great
do u know how to solve this?
yes
ok do it
x^2 - 5x -12
i just noticed
okay
but why did you turn the (x+1)^2 to (x-1)^2 lol
i slept for 2 hours
fair enough
because you put it that way
they just, for some reason, retained the 2
divide both sides of 2(x+1)^2 -22 = 10x by 2 you get (x+1)^2 - 11 = 5x
which is the same as we have
oh i get it
the 2 is totally irrelevent
they changed the other side
i dont know why they retained it but oh well
okay i get it now
ok
wait
solve the quadratic
do you know the log rules
there is no time
yes, what about them?
i have to get to school
understandable
also the exponents' laws for good measure, because u said earlier u didnt know all of them:
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I'm taking Calculus. For A. we are to get the domain of the functions.
For C. I don't know what's the way to solve that because our teacher didn't teach it.
is the top thingy irrelevent?
okay
is 'a' specified to you?
h(a^2+1) could fall into either of your function's cases
so we need to know if anything about a is specified
Nope. There's nothing more there.
okay so i assume they want u to generalise it for both cases
alright i guess
lets start with $h(x) = \s{x-5}$
what is h(a^2 +1) for this?
There's a bot that appeared
and i want ur answer to it lmao
Or is that irrelevant?
also im highly sus of the way u wrote this
sqrt(x-5) if x <= 5?
but thats only defined for x = 5
anything lesser than that and it is imaginary
are u sure u wrote that correctly
she is not sure
I just copied it from the sheet
neither am cuz idk the question
wait lemme check
theres no wae its complex
that was our quiz earlier. I just sneaked to copy it to answer it for later because I didnt do well on the actual quiz
i think u probably copied it wrong because the domain of h just doesnt include values lesser than 5
so
h(x) = { sqrt X - 5. if X <= 5
{ (X + 4)^2. if X > 5
find h(a^2 + 1)
i copied it right
i asked from my classmates
was it supposed to be $\s x - 5$
ask them if it is sqrt(x) - 5 or sqrt(x-5)
sqrt(x-5)
okay thats just weird then
how come?
try putting in x = 4 what do u get
in this
oh right it will be an error
He didnt teach us how to evaluate that
so i really dont know whats happening in there
I thought were just going to substitute it in 1?
yes but the definition of the function itself is ambigious...
but whatever, i digress
what i did on my paper was to just substitue (a^2 + 1) in both equation
yeah that should be it
its just where x is defined seems wrong, which is what i was commenting on
anyways we can work on the A's which are much less ambigious if you want?
yes please
okay so $\ds \s{x^2-1} + \s{1-x}$
lets consider each part of this
first of all the sqrt(x^2 -1)
do you know the domain of this?
no sorry
r we going to use the number line or the interval table there?
or they are not necessary?
i mean we can do it however u wanna
ok i can work u thru it
so like the square root function can never have whatever is inside it be negative yes?
but it can be zero?
what does that mean
yes that can be a part of a domain
why not
it depends on ur function
anyways
do u agree with this
,rccw
one more question. im really confused about this.
0 can be a legitimate output? in finding domain of function?
yes...
take the simplest function
f(x) = x
f(0) = 0
that is a valid input and output
there is nothing cursed about 0 that makes it not be able to be the input of any function
yeah
1/x, x can never be 0
f(x)/g(x): g(x) can never be 0
sqrt(h(x)): h(x) can never be a negative number
i hope this makes it clear
YESS
yes i agreee
greater than or equal to zero right?
yeah okayyy
so i want u
to solve that inequality
find the values of $x$ that satisfies the inequality $x^2 -1 \ge 0$
do yk how
ok this will make ur life extremely hard for the next few questions
just a warning
๐ญ
what is ???
1
great
positive
xo $x^2 \ge 1$
how do u get rid of the exponent?
how do i do that?
what is the square root of x^2?
x?
absolute value?
yeah!
so always positive?
and what about 1? whats the square root of 1
yes indeed
1
okay
if finding for sqrt of aything that is squared, just cancel both right?
the sqrt and square?
[
x^2 \ge 1 \Iff \abs x \ge 1
]
[
\s{x^2} = \abs x
]
so u should keep that in mind
hm?
oh wait
we are gonna continue from here
im just like
trying to keep up my pace with u so u dont get lost
lmao
but are u fine with everything up until now?
is x^2 - 1 the same as (x-1)(x+1)?
its another method? ๐ญ
can we try urs first?
r u fine with this
with this
ye do u understand everything
yes
with it
sick
so
lets use our definition of an absolute value function
[
\abs x = \begin{dcases*}
x &if $x \ge 0$ \
-x &if $x < 0$
\end{dcases*}
]
you know this right?
omg noo ๐ฑ
what? 
really noo
okay so
its really simple
what its saying is that
if x is bigger or equal to 0 then the value of |x| is just x
like |3| = 3
|4342424| = 4342424
is this fine by u?
yepp
yeah so the second part
is saying like
if x is lesser than 0 then its equal to -x
sooo
|-3| = -(-3) = 3
|-3424324| = -(-3424324) = 3424324
the negatives cancel so u just get the number
does this make sense
so just everything under absolute is positive no?
ok ok hehe
yeah so u get what this means now i guess?
yeah ๐
okokok
so back to what we have
|x| >= 1
so
we can seperate it into two cases
[\begin{cases}
x\ge 1, \q x\ge 0 \
-x \ge 1, \q x < 0
\end{cases}
]
this may seem confusing, but what i did is use this pretty much
ask if anything doesnt make sense lol
the second part still confusing hehe
hmmmm
so like do u agree that a negative number multipled by a negative is positive always
-(-x) = x
yes
yuh
so thats what its saying
its basically saying
if you have a number lesser than 0 (for example -3 )
then that number is equal to -x (so -(-3)) which is equal to 3
yes
ok so back to this
for $x\ge 1, \q x \ge 0$, i want you to find the intersection of both intervals
i want more than 0 apples, but i also tell you i want more than 1 apple, so in conclusion i want more than __ apple

