#help-0
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I need help
Answer to your well worded question is 7
Glad I could help
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
So, My teacher, Ms. Parry, told me to try and learn what polynomials are right, and so I need help trying to solve for them
I just need help on how to solve for them
I don't need to know your teacher's name.....
I know
Cause that's personal information
But anyway, I assume you've googled for information.
So..... what's your question?
Hold on
Cause there are plenty of resources online which can actually teach you.
yeah, that's factoring
I need help on it
Ok, post your attempt at factoring it
You looked up resources online
And taught yourself it
"How to factor quadratics" will more likely than not be very fruitful.
Is this a good video?
This algebra video tutorial explains how to factor difficult quadratic equations by using the quadratic formula in a reverse mode.
New Algebra Playlist:
https://www.youtube.com/watch?v=nTn9gVqRfKY&list=PL0o_zxa4K1BUeF2o-MlNpbRiS-oE2Kn6J&index=2
Access to Premium Videos:
https://www.patreon.com/MathScienceTutor
Damn, that's unfortunate
Ik
Too bad I don't know what you're confused about
This is the last day until report cards come back, last semester :((
Well
Thanks for your patronage!
Byeeee
@alpine sable close the channel then.
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AS * AB = AP * AC?
ik
Use chord theorem
i got pc is 1
?
Sum of 2 segments?
like as is ab plus bs?
what about ap
ac plus cp?
(AB + BS) * AB = (AC + CP) * AC
now plug in know values
you get PC=1, and now you can write AP=PC+AC correct?
yes
just trust me
thanks
np
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can aynone help me with this? huge thanks
$\table$
DETOX
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
do you know what a truth table is
p | -'p | p ^-'p
T F F
T F F
F T F
F T F
like this?
i am just not sure about my answers
i tried number 1
p | -'p | p ^-'p
T F F
F T F
huh
u only need 2 because p only has 2 states it can be in
p^-p in english means, p and not p, which is impossible
p cant both happen and not happen
ohhh
p | -p | p V-p
T F ?
F T ?
for c and d youll need a truth table with 4 rows
ohhh
lets see
p q (p ∨ ¬q) ((p ∨ ¬q) → q)
F F T F
F T F T
T F T F
T T F T
seems right
good job @alpine sable
p q (p V q) (p ^ q) (p V q) → (p ^ q)
F F F F T
F T T F F
T F T F F
T T T T T
oh kinda hard
i was struggling hahaha
thank u so much for ur help @silver adder
u're the best
the last one but i figured it out
i'm kinda new to this because we have no math in our last sem
i think just remember that T → F is false, and the rest is true
something true cant imply something is true if its actually false
@alpine sable Has your question been resolved?
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@silver tangle Has your question been resolved?
@silver tangle Has your question been resolved?
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Anybody know how I can solve a problem like this?
71p+1= 4a
is 73 a prime
yes
ohhhh
interesting
and that fulfills the rule of x^2 = (x-1)(x+1) + 1
(72+1)(72-1)+1
that is sneaky
will the same process work for something like 71p+2?
assuming that there is a number that fulfills that condition
More general - something that is not +1
which is the constant?
I do don't worry
I'm a bit tired haha
But anyways, what would a problem in the same format of the one I sent look like for this problem
would you work that out here so I can see another example? Just so I know what to plug in
so we have 53 * p + 9
we square root the 9
we get 3
then x = 56
so we plug x = 56 into (x+3)
we get 59
if u calculate 59 * 53 + 9
you get 3136
which is 56^2
and also
59 is a prime
So 59 is p
Nice, you think you could give me an example to work out?
hmm im having trouble with the primes part, because 89-5=84 and 89+5=94
wait no
79=p
Thx
You think you could give me one more?
Sorry haha
Thank you so much for the help!
Hmm would 43 also work for that one? I calculated p for 23 and 43 and they both come out as a perfect square and they are both prime. Once again, thank you for the help
@half stream Has your question been resolved?
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hey there
Ok sooo
I know its a pretty basic question
but please, if anyone could help me with that I would appreciate it
I guess I need to use the dimensions property that dim(U+W) = dim(U) + dim(W) - dim(UcapW)
@tawny fable Has your question been resolved?
@tawny fable Has your question been resolved?
@tawny fable i think you can show that dim(W)=dim(U) by showing v1-w,...,vk-w are linearly independent. but I'm not 100% on that
if you do figure it out please ping or dm me, I'm curious to see if my solution is correct.
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How do I do question 5?
have you made any progress so far?
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✅
@opaque inlet you would do well not to just close the channel immediately on me. it's kind of rude.
if you do not need any more help then at least have the decency to say "sorry, i'm already done"
@opaque inlet Has your question been resolved?
try letting $x as the full price and build an equation base on that
I’m not sure how to tho
Just with the variable x?
Wouldn’t we need y as well for the remainder
Wait
so the 50 wine are divided into 2 group
25 of them is full price ($x)
25 of them is 40% off
can you use a way to represent 40% off with x?
25x + 25 * 0.6x=2260?
Sorry about the 0.4, I wrote 0.6 in workbook
thats correct now
good job
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154x-135y=0 how should i find p and q if px+qy=0 assuming p is a prime number
prime factorize
oh gg
hmm, still stuck tho... @pale kestrel
<@&286206848099549185>
<@&286206848099549185>
@rough salmon Has your question been resolved?
<@&286206848099549185> someone plzz help
prime factorize them
do you know how to prime factorize
what work should i send?
after i prime factorize, what should i do?
sry for the late reply btw
do you get prime no.s
heh nvm, the question i asked is derived from another question, n i got the nums wrong, soooo sry 😅
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How do I solve this system in terms of a and b?
I tried putting it into row echelon form and got y = 1/4 b, but this confused me more
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Vector calculus notation question: given F,G vector fields, does G(div F) mean G . (div F) [where . is the dot product]?
I've been trying to understand the expansion of curl (F x G)
@grave matrix Has your question been resolved?
div F is a scalar, so there's no need for a dot product
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I don't know what to do to the matrix to bring it to echelon form (if that's the right way to go), pls help
Do you know the determinant
no, what is that?
Then did you learn about matrix
Yes
Good
but i don't know what to do to the matrix to find k
Consider the square system of linear equations $Ax=b$ with $A=\begin{pmatrix}9&k\k&1\end{pmatrix}, b=\begin{pmatrix}9\-3\end{pmatrix}, x=\begin{pmatrix}x\y\end{pmatrix}$ where $k$ is an unspecified real parameter.
First do you understand such notation
Yes I understand
Good
But what do you have Ax = b?
Oh wait
Trenton
Yes I understand that
The determinant of $A=\begin{pmatrix}a&b\c&d\end{pmatrix}$ is denoted by $det(A)$ and is defined by $det(A)=\begin{vmatrix}a&b\c&d\end{vmatrix}=ad-bc$
Trenton
so is that 9y-k^2?
When there is no solutions or infinitely many solutions, you have $det(A)=0$
Trenton
Not really, y is not included
Well if you want unique solution for the system, you should set $det(A)\not = 0$
Trenton
Otherwise, $det(A)=0$, which implies there are no solutions or infinitely many solutions.
Trenton
oh i get it now
but what does a determinant mean?
You should try to compute such k into the system
Cuz u dun know whether it is the case of infinitely many solutions or no solutions, unless you put back into the system
I just did that and I got -9 = 9
You can think it as a characteristic of the square matrices
?????you mean k=9 or -9?
I got k = 3 and computed it into the system which gave me -9 = 9
Ic
Is that proving that there's no solution? Or did i make a mistake?
Alright you should get k=3 or -3 if you are correct
K=3 for no solutions
K=-3 for infinitely many solutions
why are you also saying -3
oh ok
What do you equate the determinant to for finding k = -3
Well
What is the determinant?
9-k^2 right?
Set it equals to 0
$9-k^2=0 \iff 9=k^2 \iff k=3$ or $k=-3$
Trenton
Ok
how do you know that it's just 3 for no solutions and -3 for infinitely many solutions?
When there is no solutions or infinitely many solutions, you have det(A)=0
Did you understand this?
If not then it will less easy to explain
I just accepted it. I don't really get why that's the case though.
Have you done linear transformations
would you please explain it anyway?
So you have seen different types of matrices
and what geometrical transformations
they are meant to represent?
Yes
Ok, so take your 2x2 matrix.
Oh wait --- are you familiar with the geometrical interpretation of determinant
If I take a 1x1 grid square in my original plane
The area of this square after a linear transformation on the plane is the determinant of the 2x2 matrix
This generalises to higher dimensions (1x1x1 cube in 3d, etc).
ok
and then what's next?
no
Did you know a matrix has an inverse if and only if the determinant is non-zero
i knew this:
If a matrix is invertible, this tells you the transformation is one-to-one
Right and if the determinant is 0, this is undefined
If a matrix is invertible it tells you that you can 'undo' the transformation
This is because no information is lost. Each point maps to exactly one point in R^2 and no two points map to the same
What R^2? Row 2?
This sounds very familiar to the conditions required for there to exist a proper inverse of a function
Maybe it's the same thing
$\bR^2$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
What's 2R
This is the plane
R^n means nth dimension
Have you seen this notation?
Its all the (x, y) coordinates
in the plane
nope
Sorry I haven't got a good grasp on what you have or haven't seen
😅
$$\bR^2 := {(x, y) : x,y\in\bR}$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
I don't know if you have seen set notation either
if not, then this won't help
It is the set of all points written as (x, y)
Or alternatively all 2-dimensional vectors
I've seen the notation but not the R^2 (I understand what you are trying to say though, I just haven't come across the concept of R^2 as the set of...)
Ok, (am thinking a bit how to explain sry)
So if the determinant is 0
The image of the transformation is either a point (the origin) or a straight line
Is this familiar or no
yes vaguely familiar
Right and this is where the justification for infinite or no solutions is
We have
Ax = b
b is a point on the plane after we applied transformation A
Let's say the determinant of A is not 0
Then we know exactly one point maps to b
and we can invert the transformation by multiplying by the inverse of A
$$A\bs x = \bs b$$
$$A^{-1}\left(A\bs x\right) = A^{-1}\bs b$$
$$(A^{-1}A)\bs x = A^{-1}\bs b$$
$$I\bs x = A^{-1}\bs b$$
$$\bs x = A^{-1}\bs b$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
The last line gives you an exact 'formula' to get the solution x
it is A^-1 b
This happens whenever A is invertible. This means there is exactly 1 solution
When A isn't invertible, then det A = 0. This tells you the image of the transformation is either a line or a point
What about when there are infinite solutions?
Right that's what I'm trying to say
$$R^2=\left{\begin{pmatrix}x\y\end{pmatrix} : x,y\in\bR\right}$$
$$\tn{im }A = \left{A\begin{pmatrix}x\y\end{pmatrix}: x,y\in\bR\right}$$
im A means 'the image of A'
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
Thank you, but I don't understand how to use that to solve this:
So imagine this picture
If the image of A is that line, then how many solutions there are depends on where b is
If b isn't on that line, then there are no solutions
If b is on that line, then there are ??? solutions
This is the infinite case.
(I wish I explained this better
)
Yeah i understand the graphic explanation. But how do I show this in my calculations?
So firstly you need to calculate the determinant of A
that is.........
(9 x 1) - k^2
9-k^2
thank you anyway 😄
There is a unique solution
Is that good?
So that solves part c)
If it is 0, then you either have no solutions, or infinite solutions
Does that mean I equate it to not zero (for a unique solution)?
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
Or you can equate it to 0
then unique solutions is whenever this is false
So k = +- 3 gives 0
everything else gives not 0
So k isn't 3 or -3, then we know there is a unique solution
OHH okay
Next, if k is 3 or -3, you have to do some thinking
It relates to this picture in a way
The image of A is either a line or the origin
If you have a 0 determinant
It is the origin only when A is the zero matrix (matrix with all entries 0)
Otherwise you get a line
Does that make sense?
So in this case, you don't have the 0 matrix for sure, so im A is a line
You then need to figure out if the image of A includes or doesn't include b. Which is (9, -3) here
You do this by solving the equation system
I substituted k = 3 into the system and ended up with -9=9
Right
So there must be no solutions
$$\begin{pmatrix}9&k\k&1\end{pmatrix}\begin{pmatrix}x\y\end{pmatrix} = \begin{pmatrix}9\-3\end{pmatrix}$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
Well you don't need matrix you can work with linear equations
(probably easier)
then you sub in k = -3
how do you say that? Is that based on the answer that -9 cannot equal 9?
You can say the system is inconsistent
if k = 3
because you end up with 9 = -9
This is impossible, therefore there are no solutions
Right okay 😄
9x + 3y = 9
3x + y = -3
=>
9x + 3y = 9
9x + 3y = -9
=>
9 = -9
Therefore there are no solutions for x, y
Next, you solve the system for -3
9x - 3y = 9
-3x + y = -3
yup and x=1
no no
Can you see the 2 equations are the same?
If you multiply the bottom one by -3
you get exactly the top one
(or divide the top by -3)
9x - 3y = 9
-3x + y = -3
<=>
-3x + y = -3
-3x + y = -3
<=>
-3x + y = -3
So the system of equations is equivalent to just one equation
So now you know (x, y) is a solution to the original equation if and only if -3x + y = -3
oh okay
There is 1 equation, but 2 variables
Once you find out that the equations are the same, geometrically there would be two overlapping straight lines
and that means there are infinite solutions!
Ya
That means for a unique solution, k cannot be +3 or -3
Thank you so much @zenith compass @pale kestrel !!
Note that geometrically, no solutions is just two parallel lines
And also you know what happens when k = 3. and k = -3
You are welcome
when k = 3, there are no solutions, when k = -3 there are infinite solutions (based on substituting each k value into the system)
yes
There are 2 geometrical pictures you can consider. The linear transformation of the matrix itself. And the individual rows as linear equations y = mx + c
(I think they coincide in some way but uhh don't confuse them)
so next time, I have to equate the determinant to 0 and see how it goes
Basically yes.
what happens when I don't have a square matrix?
This is a bit more tricky
we cannot talk about determinant
But you do the same thing
You attempt row reduction
into row echelon form?
how though?
I tried doing that for the same question and I didn't know how to go about
Let me write an example
3x + ky = 3
kx + y = 4
-kx + 3y = -2```
might be a stupid example 😂 let me change some numbers
Ok, so row reducing what might your first step be
one moment
i mean row 2 + row 3
ah sure
sorry 😅
So you are applying rule 3
ok
3x + ky = 3
kx + y = 4
4y = 2```
yeah i understand
Ok, then next is a tricky part
You want to eliminate either of the x
If you divide by k, you need to split into 2 cases, k = 0, or k not 0
Uhhhhh I usually would be systematic about row reduction
although you could
I would usually first eliminate all the x's possible
then all the y's
ok
and so on
(note that sometimes is not a good idea when there is some shortcut)
So you want to eliminate either x
ok
I would advise using rule 3 again
3x + ky = 3
kx + y = 4
4y = 2```
what if you first multiply row 2 by 3 (rule 2)
3x + ky = 3
3kx + 3y = 12
4y = 2```
And then can you apply rule 3?
(You could have divided row 2 by k, but you want to avoid that basically - splitting cases early on means more math)
Row 3 has no x
I just multiplied row 2 by the scalar 3
R2 -> 3R2
Applying rule 2
(i didnt have to, but to make things easier to see)
Then you want to kill the x's of one row
Can you add a scalar multiple of row 1 to make this happen?
k?
-k
Ah okay
3x + ky = 3
3kx + 3y = 12
4y = 2```
R2 -> R2 - kR1
3x + ky = 3
(3 - k^2)y = 12 - 3k
4y = 2```
I may have written it incorrectly
just checking first
ok
yes k could be 0
but rule 3 is very useful
because you are allowed to the scalar multiple to be 0
$R_n \to R_n + 0R_m$
i just multiplied R1 by -k
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
This is allowed
so i have -3k k and 3k
No, you cannot do that
You cannot do R1 -> 0R1
(so if you multiply by k, you could need split cases)
But this operation is allowed without needing to split cases
$R_2 \to R_2 - kR_1$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
So you are allowed to do this
are you saying that if i multiply by k and then subtract, it is allowed? But if i just multiply by k, it is not allowed?
There is no restriction on the 'scalar multiple' for rule 3
I am saying you cannot do
$$R_1 \to -kR_1$$
and then
$$R_2 \to R_2 + R_1$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
Instead, you should do
ie. leave R1 unchanged
Eliminate the x's in R2 utilising rule 3
Basically, I am following these rules exactly
And rule 2 has a condition that the scalar cannot be 0
So the first step requires me to split cases if I do R1 -> -kR1 first
The reason why you cannot multiply both sides by zero is that, if u do so, you always get 0=0 which is always true (even originally it is sth nonsense like 0=1)
ok
2x + 2y = 1
1x + 1y = 2
~
2kx + 2ky = 2k
1x + 1y = 2
~ (if k = 0)
0x + 0y = 0
1x + 1y = 2
Its something like this
if k is 0
you kindof kill an equation
And it will be ridiculous if u get 0=0, totally useless to your calculation, so we define that we can only multiply a row by non zero scalar
ok
But rule 3 is different.
now i have 0 (3-k^2) and (12-3k)
3x + ky = 3
(3 - k^2)y = 12 - 3k
4y = 2```
You should have this
yes?
So all the x's are eliminated
Next you need to try eliminating the y's
Again, rule 3 is recommended
Try
$$R_1\to R_1 + \lambda_1R_3$$
$$R_2\to R_2 + \lambda_2R_3$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
I write lambda1 and 2 for the scalars you need to figure out
It is possible to eliminate the y's in Rows 1 and 2 this way.
One moment I have a question
(Ah the pains of explaining through text linear algebra 😂 --- much easier in person)
because 3 is not 0
But for multiplying a row by k, it has to split?
because k might be 0
Also, instead of multiplying R2 by 3
and then R2 - kR1
I could have done something else
$$R_2\to R_2 - \frac{k}{3}R_1$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
I multiplied R2 by 3 just to avoid fractions
This step alone would achieve the elimination of x
So you could have done this first and then R2 -> 3R2 to get rid of the fractions
So technically, the 2 steps we did is this
$$R_2\to 3R_2 - kR_1$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
This is allowed, because this applies rule 2 (multiplying by 3) and then rule 3 (adding -kR1 to R2)
OR
rule 3 (adding -(k/3)R1) and then rule 2 (multiplying by 3)
$$R_2\to 3R_2 - kR_1$$
$$R_2\to 3\left(R_2 - \frac{k}{3}R_1\right)$$
𝐒𝐡𝐮𝐫𝐢𝟐𝟎𝟔𝟎
Either works (which represents 2 steps)
So I suggested this
let me see
3x + ky = 3
(3 - k^2)y = 12 - 3k
4y = 2```
I don't think so
You should apply row transformations in this form
oh yeah i remember 😄
The reason I am doing it like this is to avoid multiplying by k...
I don't know if that is clear to you
Why I decide to leave R_3 unchanged
and eliminate y from R1, R2
If I tried the other way round, case splitting would be necessary.
some scalar constant
you need to find
So let's think about the first one
R1 -> R1 + ? R3
What multiple of R3 would eliminate ky from R1
3x + ky = 3
(R2)
4y = 2```
4
-1
ky - 4y makes (k-4)y which isn't 0
ky -> ky + a(4y) = 0
ky -> ky + 4ay = 0
4a = -k
a = -k/4
Would this thinking help?
The top is what we want. The bottom is what we need in order to make it happen
So just one last thing
You might have examples where splitting cases is unavoidable
1x + ky = 3
2ky = 1
In this case, to eliminate the y's
You have to divide by k no matter what
ok
So you split into cases.
how
Suppose k = 0
1x + 0y = 3
0y = 1
Ok, this was kinda a dumb example, so this automatically eliminates y
I will change the example to this
1x + (k+1)y = 3
2ky = 1
Because both y's have a coefficient involving k in them
You will have to split cases in order to eliminate.
Suppose k = 0
1x + 1y = 3
0y = 1
(Ok there was no point changing the example, nvm)
Then this gets you the answer
Suppose k isn't 0
1x + (k+1)y = 3
2ky = 1
Now you can divide by k
1x + (k+1)y = 3
2y = 1/k
And then I can subtract (k+1)/2 of R2 onto R1
R1 -> R1 - (k+1)/2 R2
1x + 0y = 3 + (k+1)/(2k)
2y = 1/k
Then this gives you the solutions
Maybe there's a good video online/tutorial explaining this 
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Solving steps, please?
Here’s my attempt.
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hmm that's weird
mhm
?? I’m not the best at trig identities
Yo mamas weird :/
yeh i agree
thats the answer i put
Oh, I didn’t see the incorrect part!
and it said that i was wrong >:C
LMAO
very weird indeed
the machine is drunk or some
so many different ways to show that the answer you have put in is right yet the "system" says it's wrong
anyways
i also thought this answer was correct but system says otherwise
this problem takes more steps so i prob made a mistake but i solved it three times and got same answer 
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hey so i'm just wondering how to factor polynomials of degree three. For example, x^3 + 2x^2 -x -2
i was told that all the possible factors of this polynomial is the factors of the final term
do i just use synthetic division with all of the possible combinations until i find one?
please ping me when you have an answer
well, what people probably meant by this is that the rational roots of this polynomial must be divisors of the last term
yes, that's what I meant
Since the last term is -2, the only possible integer roots of the polynomial are 2, 1, -1 and -2
Assuming we have rational roots then sure
ok so i try synthetic division with 2, 1, -1, -2?
sure
so uhhhh
let f(x) = , x^3 + 2x^2 -x -2
f(2) = (2)^3 + 2(2)^2 -2 - 2
so i just check if this is zero? @pale kestrel
yes
ok i can take it from here
if this is 0, then x - 2 is a factor
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how do I solve (ii)?
there are n! bijective functions between M and M so we have 6 functions in this case
But how should the operation table look like?
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Is this correct?
the 1/2 is multiplying (v_0+v)t so I don't think you can just subtract it to the other side
if that makes sense
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If a graph intersects the x-axis then the coordinates used to formulate the tangent will only be (x,0) right?
This is not a textbook question or anything i just want to know for sure before solving an exercise
If the tangent is at that point, sure
yes, I think so
Yes, thanks!
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Why do we ignore the square root sign when integrating
What do you mean?
I mean why do you not take the absolute value when taking the square root when integrating
Give a concrete problem or example
When we integrate $\int \sqrt{x^2} dx$ we get $\int x dx $ not $\int |x| dx$
S̴̤̃e̶̪͗e̵͉̋
Ah that, so afaik (other ppl may add more), that's just mathematical convention I think. Square root in general refers to only the positive roots
I don't think mathematical convention explains that
You need the modulus sign when square rooting something that has been squared in general
There's a deeper reason relating to functions too, I think. So, a function always has to have only one y value per x, if you took both possible roots, it'd mean there's more than one y value for a given x so you just take the positive ones I believe
But to just take the positive root, you need the modulus sign
As x may be negative
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$\int_{-\infty}^\infty \frac{\sin^2x}{x^2},dx=??$
Apparently the answer is $\pi$. How?
The antiderivative is non-elementary, so there must be some sort of 'trick'. But the most common trick for integrals like these, i.e. the residue theorem, doesn't work since there aren't any simple poles. So I don't know how to tackle this now. Please help!
idioticbaka1824
Umm Fourier Transform?
Complex analysis works too
i totally forgot about the fourier transform. lemme look up how it works again real quick
wait a sec, isn't fourier transform mainly for solving DEs?
Fourier transform is more versatile than that
But you're probably thinking of Laplace transforms
They're nearly identical anyway
oh wait yeah there was like parseval's theorem or something
the FT preserves inner products, so let's see if we can rewrite this as an inner product
oh man, i spent a while puzzling over the FT of sinx/x and eventually found an answer on stackexchange - you need to IFT the sinx/x to get a little box-like function. who would've thought of that?
anyways thanks a lot!
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Hi, I'm currently doing a recap on sequences (I did this two years ago, but it's completely slipped out of my head and I feel idiotic)
I just want to get a better understanding of formulas
I'm supposed to 'Write down the formula for the nth term of the following sequence: 1, 3, 9, 27, 81
I mean like there are potentially infinite sequences
How so?
I mean like you can construct any n > 5 degree polynomial
It's obvious what they are looking for though.
Ah right, Arithmetic, Geometric, Polynomial sequences, I believe this is geometric (Multiplication)
Yes, what's happening between each element?
It's multiplying by 3 (1x3 = 3, 3x3 = 9, etc..)
I was going to put 3n as the formula, but since it starts at 1, it can't be that
you mean 3^n?
no I meant 3n because it goes 3 then 9, but like I said it can't be 3n since it starts at 1
3*n would mean the sequence would go 3, 6, 9, 12
3^n would mean element 1 is 3, but... it's close
oh. my mistake sorry
no worries at all!
when writing the formula for the nth element we completely ignore what the element before was etc.
ahh okay I wasn't aware of that
yeah I think I understand
since you ignore the element before, would that be 1?
yeah, it's a completely standalone expression
1 is correct
now, one could argue that the first element is no. 0
but lets assume they want us to solve it as if the first element is no. 1
programmer moment
also polynomials and many nice summations
hm okay, that's good to know thanks!
but you see how 3^n is correct, just shifted one step?
sort of, yes
so where we have element n right now, we want element (n-1)
i'd write out the sequence to visualize it better
wait sorry I'm kind of confused what do you mean by this?
well, if we write out the sequence for 3^n we get
element 0 is 1 (3^1 = 1)
element 1 is 8 (3^2 = 8)
element 2 is 27 (3^3 = 27)
yes, good
but if we want the sequence to start from element 1, and element 1 to be 1
any idea what we could put?
or wait wait wait a sec that's not correct
element 0 is 1 (3^0 = 1)
element 1 is 3 (3^1 = 3)
element 2 is 9 (3^2 = 9)
3 times itself 0 times is 1
it's not 0 x 0 x 0
3^4 is 3x3x3x3
but 3^0 is just 1
that's just how it is
no worries
3 is base, n is exponent
first element is 1
second element is 1x3
third is 1x3x3
fourth is 1x3x3x3
got you
perfect
first element n=1, but we want some exponent which is 0
i don't want to give you the answer directly but i think i will, just make sure you look at it properly anyway, ok?
that's fine
I just want to understand this better
okay so the general expression is 3^(n-1) if we want the first element to be 1
oh I get it
if the expression is 3^n you get
n | 0 1 2 3
3^n | 1 3 9 27
if the expression is 3^(n-1) all elements shift to the right
n | 1 2 3 4
3^(n-1) | 1 3 9 27
does that make sense?
will do, thank you, if you don't mind, can you explain why that is?
yeah
maybe you'd expect a^0 to equal 0, but 0 is special
1 is kind of like a factor of every number
yeah
so when you times by no a, it's still 1?
i think there'd be examples to show you why it is this way. but it is just a definition.
hmm ok
well I searched up an analogy for it,
"How many ways are there to place a penny, a nickel, and a quarter on the table such that no coins are on the table? Again just 1."
If there are no coins on the table, there is only 1 way to arrange them
I think that's a good way to remember it
that's a good way to think of it!
well, thank you very much for all the help! I really appreciate it
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hello, help me please with this IQ question, i can't seem to find the pattern in any way.
nevermind i found it, what about this one
they're testing OUR iq.. ?
||(2+6)*(5+7) = 96, (5+8)*(3+4) = 91||
@ancient sedge Has your question been resolved?
Hey, not really universities in turkey require students to study for IQ and math exams for university entry, so we literally take ideas about IQ questions lol
thank you guys
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Need a little help finding the area of this thing!
You have a big rectangle and 4 triangles
oo just add triangles to make a rectangle?
In this case yes
find the area?
6cm
like the sides are 6cm
How exactly are you finding 6
