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1 messages · Page 259 of 1
say that the first term wasn t 1
we can t do it ?
if it just continues to go up the same way?
Can't do what exactly?
if the first term was like idk 33
can we not calculate the sum till u90?
with the formula
if it goes by the same way
If we are given or are able to evaluate the common ratio, then we definitely can calculate the sum
with the same formula*
Simply plug in u0 = 33, n = 90 and q = whatever q is into the formula
?
Yes
No, the value of the first term, even if it isn't 1, doesn't change the way the sequence grows/goes up
okii perfect thank you u just enlightened me
and now back to the exercice if ur okay w it
here
Yeah, right
Since we have derived this earlier: [ 1 + q + q^2 + \dots + q^n = \frac{1-q^{n+1}}{1-2} ] We can simply plug in $q = 2$ and $n = 63$
A Lonely Bean
That gets us the same thing as what the solution in your screenshot says, namely, [ 1 + 2 + 2^2 + \dots + 2^{63}= \frac{1-2^{63+1}}{1-2} ]
A Lonely Bean
and how do they simplify it to 2^64 -1 please
1 - 2 is just -1 and dividing by -1 is the same as swapping every term's sign
So 1 - 2^64 turns into -1 + 2^64
Yes
wow thank you so much for ur patience LOL as last question the formula wouldn t work the way we want if we don t consider the n+1 right ?
it would just mix our mind and give us q^n+1 of what we wanted right
automatically
if we did like q^64 it would have given me q^65 instead ?
If the sum was up until q^64, then the formula would include q^65, yes
You are welcome 
I am going now so if some doubt comes up about what we've discussed just ping me and I will see the message later
Good luck
oki perfect thank youuu small detail i wanna know how will the first term starting at whatever number appear in the formula please ? @sage geode
@tacit sorrel Has your question been resolved?
It will just be $u_0\cdot\frac{1 - q^{n+1}}{1-q}$
A Lonely Bean
Because, again, every geometric sum is basically $u_0(1 + q + \dots + q^n)$
A Lonely Bean
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Can anyone help me with this? I dont understand how to do it.
@glacial widget Has your question been resolved?
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Why did they multiply row/ column of A? Why couldn’t they have multiplied the row/column for B?
@indigo pendant Has your question been resolved?
@indigo pendant Has your question been resolved?
Whenever you multiple matrices, you take the dot product
So you multiple each element by the corresponding element and take the sun
You always multiple row by column
so the first row of matrix 1 by the first column of matrix 2
In prolem B, You go column by column before switching rows (theres only one column in matrix 2 so we switch to row 2 of matrix 1)
we continue until we have a new matrix
heres a helpful representation
We continue multiplying row by column, before switching rows when we run out of columns
We slowly can build and answer
Switching the two matrices and multiplying gives a different answer because we are multiplying a different row by a different column
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anyone know how to solve this?
I don't think that derivative is correct
yeah that's not what you wrote
yeah
wdym by delta y
Also (-1/4) * (-1/4) is 1/16 not -1/16
it said approximate f(2.25)
so I thought it meant like like the diff of f(2.25) and f(2)
I think I just don't understand this question like what exactly does it want from me
i think its asking for a linear approximation
when you find the tangent line to f(2), you create a linear (straight line) approximation of the curve near a = 2
so once you find the equation of the tangent line, L, you find L(2.25)
^
did I get the right tangent line ?
-1/4(x)
its not as hard as you may think

son calculus only gets harder from here 😭
Yep
na son I am just gonna ff the course
for real though, this is still baby's first steps for calculus. i wouldn't even consider it calculus until you get to integrals. everything prior is the "buildup"
this is really all you're doing for this problem

finding L(x) and then plugging in 2.25
guy I am like ONE week into my first year of uni
ME TOO
guy
- I’m challenger
I don't think you understand my school was not good at teaching calculus
+I am unranked
Why not
I don't play leauge that often
i had to learn english and learn math at same time sooo
womp womp
1/
@mild stirrup Has your question been resolved?
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hello there i solved this one
but when i enter it online for my assignment it says that its wrong
this is what i entered
says its incorrect
i didn't get it
MellowDramaLlama
bingo
omg thanks
yeah sure
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why is 1.75 false for the first one
1.9 *
isn't it in the margin of error
why is 1.9 incorrect
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@sweet sparrow Has your question been resolved?
.vlose
.close
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I don't know if I'll ever get this
I might have to switch majors xd
I'm so stupid it hurts
you need to solve the equation Ax = 0 I guess
I mean yeah
with 0 the zero matrix 3x1
what does "mapped into" even mean
A represents a linear transformation
Like a function f, for a given x, you get f(x)
I don't see any connection to that and my question
its just fanciness for matrix multiplication
you wanted to know what "mapped into" means, so I gave an example
Ax = b, means you multiply matrix A by vector x. You can say x gets mapped to b by some linear transformation with A, i.e x -> Ax
so the question is asking what x values result in Ax =0?
yep
I wish they'd just said that but
okay
that's a start
so
the answer to this question
is very confusing to me
if these vectors match up columns to rows
why are there two of them
why are we adding them
and why are they named 3 and 4?
I think the first column vector gets mapped to zero and so does the second one
v1 = [ 8 4 1 0 ]
v2 = [-6 -2 0 1]
Av1 = 0
Av2 = 0
so Av1 + Av2 = 0 + 0 = 0
A(v1 + v2) = 0
Av1 * x3 = 0
Av2 * x4 = 0
A(v1 * x3 + v2 * x4) = 0
Not sure why they named those x3 and x4 its probably in the way they found these vectors
but I forgot how to do everything numerical with linear algebra lol
after you row reduce A, it has you do this:
I understand the part where we're talking about the variables in terms of free variables
they lose me where they start turning these equations into a fucking vector
makes ABSOLUTELY NO GOD DAMN SENSE
so I don't even know what this notation means
and clearly it's trying to make sure no one knows what it means
so the solution should be a vector right
Ax = b (x is a vector and so is b)
so when they say Ax = 0 they mean the zero vector
right
you know what confuses me
why is this
suddenly
different
than plugging in x_1 x_2 x_3
like
earlier in the class
that's how Ax=b worked
now it's this whole
different thing
when we were using a matrix as a set of linear equations, x_3 was either one value or another
how can it be 4 different values?
what the fuuuuuuuuuuuuuuck
the x vector should look like
[x_1]
[x_2]
[x_3]
[x_4]
not this
so
So
A x = b
Where x = [x1 x2 x3 x4] and b = [b1 b2 b3 b4], since they are both vectors
However when you did the augmentation thing we noticed that when x1 = 8x3 - 6x4 and when x2 = 4x3 - 2x4 we get Ax=0
So now x = [x1 x2 x3 x4] = [8x3 - 6x4 4x3 - 2x4 x3 x4]
Which is the same as saying
OH.
[8x3 4x3 x3 x4] - [ 6x4 2x4 0 0 ]
then x3 * [8 4 1 0] - ....
try not looking at the solution and getting there yourself
nah I understand it now
it is kind of a single vector
it's just
visually deceptive
because of the free variables
thanks for writing all that out
idk how
but it made it click
exactly
it is a single vector they just made it a sum of two vectors
I just solved a similar question on the first go
makes total sense
thanks a ton @unreal atlas
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im not sure where to start
do you know how to graph functions y = ax + b?
Use y = mx + b, plot both equations
i need help guys
Then you limit it
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whats the difference between an open circle and a closed circle in terms of like plotting points
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This is a very stupid, quick question, but I'm having a bit of confusion regarding this stack overflow post regarding convexity using the hessian:
To be specific, my question is this:
Is x just [f(x,y), f(x,y)]?
The equation in the post I think is wrong, but I just wasn't too sure exactly how they got a normal function into a vector
Unless it's just [f(x,y), f(x,y)]?
@fast knot Has your question been resolved?
<@&286206848099549185> (It said I can use this ping after 15 minutes)
@fast knot Has your question been resolved?
@fast knot Has your question been resolved?
No, x = (x, y). The post should have used vector or bold notation on the left side
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Hi , I need help with this question. I don't think I know how i should approach this question. Thanks!
@light depot Has your question been resolved?
<@&286206848099549185>
Hi
I need help with Indices
anybody can help i also need some help with LCM and HCF problems!
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Five consecutive terms of an arithmetic sequence have a sum of 40. The product of the first middle and last terms is 224. find the terms of the sequence.
What step are you on
I have no clue where to start
Or what equation to use
my tutor gave me these two equations
!status
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
a, a+d, a + 2d, a + 3d
a constant rate of change between terms
Yep
No
a, a+d, a + 2d, a + 3d = 40?
ohhhh
Oh sorry
Mb
Yeah
The sum
Of all the terms
@soft stratus
First, what are all the five terms
These are only four terms.
would i set it up as
(a-2d) + (a-d) + a + (a+d) + (a+2d) = 40
Your choice
5a=40
a=8
oh crappy myb
does
d=radical 40?
wait no
no
wait
idk
brb
help
@autumn adder
did i do this right
i redid it agin
<@&286206848099549185>
seems fine
I could recommend taking the 8 to the other side, but nonetheless will yield the same result if done correctly
Huh?
No
$$(8-2d)\cdot (64+16d)=224$$
$$8\cdot (64+16d) - 2d\cdot (64+16d) = 224$$
what did i do wrong. 
How even will the d term cancel
okay i will do this
You're welcome
Now find the terms by plugging in values 🙂
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what is the quickest way of solving these questions without a calc?
just finding the critical values and doing some sort of sign diagram?
Ideally you want to eliminate the denominator on both sides
that would eliminate some solutions
you can compensate for it afterwards
yep
Consider cases for when it's positive and negative
first we'll assume x > 1 and x <-3
that makes both the expressions positive
cancel out the denominators and solve for the solution set
No such x exists
Or instead of and
that's a different story
whether any solution exists in that range or not
I'm just saying we go step by step
then we'll assume x is between -3 and 1
flip the inequality signs because the expressions are negative
then solve
you have 3 cases. x < -3, x >1 and x between -3 and 1
correct
yes
Considering cases that don't exist is not a good use of time
so just sign diagram those cases?
The denom will be positive or negative in each case
Sp u flip the sign if needed and solve the quadratic inequality
yes
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ok thanks
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is this a mistake?
I thought for Euler's totient function, we have $\varphi(pq)=(p-1)(q-1)$
Kalgar
So shouldn't it be $(2-1)(2-1)\cdot (5-1)(5-1)=16?$
Kalgar
@clear kraken Has your question been resolved?
what is phi here?
no, it's phi(pq) = phi(p) phi(q) if p and q are coprime which is the first step
then phi(p^k) = p^k-p^(k-1) if p is prime
which is the second step
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againg Pythogoras
i dont get it
make a diagram first.
i did
show your diagram
ok
angle XPY is 90*
well no sh*t
brb
aight calm
is the answer 148 degrees and 51 minutes
the angle in the triangle is tan^-1 (950/420)
so the bearing is 360 - 145 - tan^-1 (950/420)
= 148 degrees and 51 minutes
,calc 360 - 145 - atan(950/420)*180/pi
Result:
148.85047390808
,calc 0.85047390808 * 60
Result:
51.0284344848
ok yeah checks out
aight thx
@fluid gulch Has your question been resolved?
hello jeppyma
familiar friend
i didn't think u would need help for trig
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Did I do this right? Help me with finding the domain and range of multiplication of functions please.
it's like f(g(x))
so sqrt (g(x)+2)
Ah, no. I'm sorry for the dirty handwriting, but it was supposed to be written as f•g, not f○g.
do you mean multiplying or composite functions
Multiplying.
oh
then i think youre right
wait
how did you get the range of y
Uh, wait. I don't know how to explain.
I plugged in 0.4 in the function, and got -5.948 as the lowest result.
Can you see?
it might be 0.41928902809
you cannot get the exact answer by that method
we have to use differentiation to find the exact value
How did you get 0.419... ? Also, I don't know how to do differentiation.
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@light oriole Has your question been resolved?
@light oriole Has your question been resolved?
Please can someone help me here with simplifying polynomials I know my answer is wrong but I’m not sure where I went wrong
,rotate
correct
.close
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2n+2 = 2(n+1)
they divided the n+1
Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaarghhhh
(n+1)² = (n+1)(n+1)
on the denominator you have 2n+2 = 2(n+1)
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Need help on this
The only hint I have is that I got to use the intermediate value theorem
Im stuck at f(1/2) I don’t know how to calculate it
Why do you need to calculate f(1/2)
Because according the the ivt I have to show that g(1) x g(0) is negative
And g(x) = f(a+1/2) -2-f(a)
If I substitute I got the f(1/2) left
So I need to get ride of it
I thought about changing the interval and taking <1/2,1> since it’s in <0,1>
Do you understand me ?
So I’m stuck at calculating g(1) and g(0)
This is a sneaky one
Basically you gotta show that 2 is contained in the interval bounded between f(1/2) and 4 - f(1/2)
And after that it's a straightforward application of the IVT
I tried to use the corollary
What corollary
sorry i didn’t get it
Well nvm
What part don't you get
Maybe try a different g
No I got what u said but I don’t have any clue about how to show that 2 is between f(1/2) and f(1/2) -4
I don’t think so ?
What can you say about the arithmetic mean (a + b)/2
A center ?
Yes so I will use another interval ?
Yes, take a = f(1/2) and b = 4 - f(1/2) for instance
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Hi. It’s not a question in some work book or anything, I just want to clarify what average is.
Here’s all many students that ATTENDED throughout 4 days of school. Meaning 4 days of school passed and below are numbers of each student that how many days already attended.
4
4
4
4
4
4
4
2
4
4
3
You would add all numbers and then divide with 11 (amount of numbers) and then again divide with 4?
Do u know the meaning of average?
Not really
!help
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Ok anyways could you tell me how would you do it
@tight patio
<@&286206848099549185>
What’s the meaning
Of average
Idk
Can u tell me
CAN U
FJRJDJKGFKKRKGKLG
@tight patio
<@&286206848099549185>
@royal basin
weh?
Ok
What’s the total number of these jumbers
Like how many numbers are there
Like
How many observations
@gilded ferry Has your question been resolved?
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not sure what I did wrong tbh
other than the second one i missed a decimal
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claim
Ok so I need some help with this , the question is that I need to find the average rate of change from 0 seconds to 2 seconds and from 2 seconds to 4 seconds and describe whats happening. Time , t is seconds.
figured it out actually
.close
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help?
use the definition of divisibility
im really not great at maths
i just put n=1
till like 10
and ig that should be enough
but apprenlty its not
all that does is show that its divisible by 1-10
and everyones trying to explain it in a complex way so i feel well dumb
mhm true
there is a very real possibility that its not divisible by 11, right? so you have to consider all cases
valid
so to do that we need the formal definition of divisibility
theres one?
yes
should i search it up?
a | b (a divides b) if b =ac for some integer c. this probably doesnt make much sense tho
gcd(x,y) ≠ 1, right?
whats gcd
so by our definition if we want to prove it formally, 5 | 15 if 15 = 5x
or 5 times another integer x
and it does! 15 = 5*3
so its a multiple? is what you're trying to say?
basically
wdym by formally please?
Greatest common divisor function
so like here are some examples
2 | 4 because 4 = 22
4 | 20 because 20 = 54
2 | 24 because 24 = 2*12
he said he isnt great at maths dude that answer likely makes no sense lol
so in math we could say
thank you 😔
like okay if i asked you "how do we figure out the next number" you could be like "well just count"
like for any number
but a lot of times, like if we want to make a computer program
its a length time taking way tho
that wont really help because computers dont know how to count
oh so algorithms is what we need
thats just a really specific example tho, this becomes useful when u have more complex statement
s
yes!
so what we could do to make a formal definition, or a definition that are unambiguous
unambigious meaning theres no confusion for anyone
we could say it like this
"to find the next number for any integer n, compute n+1"
okay back to ur problem
gotcha
🙂
so i think it might help to try a simpler problem
prove that 2n | 4n for any integer n
remember a | b if b = ac for some integer c
any ideas? if not thats fine
mhm i wanna think about it
a divided by b
if b = ac for some integer c
or 2n | 4n if 4n = 2n*c for some integer c
a divides b*
or like a goes into b evenly if b = ac for some integers a, b and c
yes
ok ok ok
so here if we want to prove 2n | 4n we just have to rewrite 4n as 2n times something else or 4n = 2n*c
so maybe 2^n - (-1)^n = k
try doing this
what would c be here
2?
yes!!!
yay
so 2n | 4n because 4n = 2(2n)
🌻
so 2^n - (-1)^n | 3
yep
bro gave me an insane amount of direction right there
but u still got it lmao
but dont i have to prove thats for all positive integers?
ive been stuck over this since mornin or sm
2^n - (-1)^n
ok
is there a way to rewrite this at all
erm
its not equal to smthn
so no ig?
unless we assume
that
x^n is =y
or smthn
1^n
okay but we have 2^n+1^n now
3^n
which is?
yes
hold on what the flip
we are try to show that 2^n-(-1)^n is divisible by 3
is this not just casework
but we just showed that 2^n-(-1)^n is 3^n
i solved it till n=10
this is not true
cant do till infinity
oh wait fuck bvm lmao
well unless you're mod 3
both of you are confusing me brub
uh no
okay so an even number is a number that can be rewritten as 2k for some integer k
an odd number is a number that can be rewritten as 2k+1 for some integer k
16 is even because 16 = 8*2
17 is odd bc 17 = (8*2)+1
this statement is really hard to prove on its own, but it might be easier if we break it up into 2 parts
since every integer is either even or odd, we can prove that its true when n is odd and we can prove its true when n is even and that covers everythijg
(it's also much easier if you do this in mod 3)
and that will be easier
i doubt he knows mods
whats mods
bc he said he struggles w math and also tried to prove it with n=1 through n=10 so
does this make sense tho
kinda
(mood)
one of my seniors said they use induction method or sm\
eek
yea
im in 9th but i've taken number theory courses before so I know this material
dang
i dont think he knows induction
me?
weird
ay i did the same thing when i was in 9th
nice
is there any way around this for me to understand and solve it
remember how i told you that every integer is either even or odd
yep
n is even if n = 2k
n is odd if n = 2k+1
ok
so try plugging in 2k and then prove its true if n is even by factoring it and shit
then once uve done that uve proven it for half of the integers
i dont think wed have wnough time
to do that
because we need to ahow its true for every integer
im gonna send you three other questions
check if those are right or wrong
then well come back to this
then we automatically half half the integers, after uve proven that try plugging in 2k+1
bevause i think ill understand comparitively better
okay
looks right
cos(π/4) = 1/√2
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can someone help me with 5a
f(x)=x^2-4
so what is f(-x)
what do you mean “put the whole thing in”
After or inside the ( )
noo…
Ok look
yes
^
plug in -x for x
?
No
What is (-x)^2
x^2
x^2-4
so i dont do anything with the 4
the question asks for -f(x) Right
What happened to the 4
no
x^2-4 right
yes
-f(x) just means you times everything by -1
So it would be…
What
Yes
u said multiply
-f by everything
so i did
i multiplied the x
what
-f(x) means -1 times f(x)
didnt they do that too
Weird


