#help-4
1 messages · Page 32 of 1
3 raised to 1/4
What do you mean by Newton's formula?
$x^2 - 3^{1/4} x + 3^{1/2}=0$
Ann
like this?
was unclear from your original msg
you can find the roots as complex numbers and then convert them into polar form.
In your original question as you posed it, the sign of the 3^(1/4) was negative
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Hi I need help
😭
use pythagorean theorem
do you know pythagoras theorem
a^2 = b^2 + c^2?
before we get to pythagoras we need to also find out how to identify the right angle in each triangle
it's generally written as a^2 + b^2 = c^2, but yeah
so far thats what Ive done but
I dont get how I'll get EG and BE if there aren't any values for them
well the idea for EG is that you focus to just the rightmost face (in which EG lives) and look at triangle EFG or EGH (your pick. if you can't pick, then EFG.)
noting that EG will be the hypotenuse of that triangle, while its legs are the known depth and height of the cuboid
so EG = 4^2 + 3^2
EG**^2** = 4^2 + 3^2.
in pythagoras' theorem, all sides are squared.
you shouldn't omit the square on any of them. it's a pretty common stumbling spot.
How about for BE?
look at triangle BGE, which is again a right triangle with the right angle sitting at G
oh actually
and now its two known sides are EG (which we just found) and BG (which is the length, 12)
its a right angle?
yes
imagine tipping the cuboid over so that face EFGH rests on the ground
then edge BG will be upright and thus perpendicular to anything that's level with the ground
incl. edge EG
sure, do you know the SOH-CAH-TOA mnemonic?
yes.
it's just this mnemonic and figuring out what goes where.
carefully mark all known side lengths and right angles in every triangle involved.
could I ask for help on no. 2, b.?
uh length of BF to be exact
bcs I got 12.64
could I ask help double checking? Cs I think it's wrong
[your pen's kinda blocking the diagram]
I'm guessin it's this one tho
But I got root(160) too, which is 12 point something yh
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need to find error bound on an approximation from simpson's rule.
Result:
2.1701388888889e-5
,calc 2.1701388888889e-5 * 3
Result:
6.5104166666667e-5
K * 6.5104166666667e-5
need to solve for K
iirc I need to find the max value of K within the given interval which is [1,4]
and choose K to be that
but I don't like graphing. could prob use calc 1 stuff to find max but I forgot, how does finding max point in an interval work again?
Result:
0.0015625
,calc 6.5104166666667e-5 * 24
Result:
0.0015625
!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
integral from 1 to 4 x^4 dx. a. find sympsons rule approximation. b. find error bound on your approximation
I suppose I shouldn't have even included this context
my question is how can I find the max point on the given interval for x^4
either plot x^4 or evaluate it for a few values of x in your domain and find a pattern then use calculus to verify your pattern
what were the calculus steps to find a max within an interval?
(I know we need fourth derivative here and the max is 24=K but I wanna know how to solve harder problems without graphing)
In this section we discuss how to find the absolute (or global) minimum and maximum values of a function. In other words, we will be finding the largest and smallest values that a function will have.
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brandon
@tawdry lintel Has your question been resolved?
@tawdry lintel Has your question been resolved?
@tawdry lintel Has your question been resolved?
@tawdry lintel Has your question been resolved?
<@&286206848099549185>
@tawdry lintel Has your question been resolved?
what is the way you use?
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I need a reminder on how to do these questions cause I forgot
I forgot how they work I need an explanation on them to jog my memory
do you know what nCr is?
which just means n choose r
I’m Pretty sure n is the max number of options and r is the amount of options that you can choose between
Like if theres 12 teachers you can choose between 7
So 12c7
Is that right?
yep 
When does it become a fraction though?
Cause in some questions it becomes like
12!/7!
that's because they use this formula
although 12!/7! is the wrong option
that’s not what I mean in like some questions the answer becomes 12!-7!/9! it’s weird I forgot how that worked
The formula isn’t what I’m concerned about
Yeah that was just an example
which question?
Let me find one rq
alright
the wording is a bit confusing but I think it's just another nCr question but you have duplicates for R?
also Darren not knowing how to spell his name is funny to me 
The answer key says the answer is 5! Over 2! Which is 60 cause of the duplicate r but I need to what else can cause fractions like these to occur
There’s a visual of it
It's dependent on what the question asks if you try to figure out what causes the fraction to occur
like the question says they already had the letter D being in front
so D is excluded
It would be 1 x 5 x 4 x 3 x 2 x1 I think but the two on the bottom I’m not sure why it’s there could you explain why?
I get it’s cause of the duplicate r but why do we divide and not subtract or smth
one hint for some weird counting that may show up: the two Rs are identical, so swapping those two Rs don't change anything and they count as duplicates
we divide instead of subtract to account for the duplicates because for each arrangement of ARREN, you can get an identical arrangement by swapping the two Rs
since they count as duplicates, each arrangement of ARREN actually counts as two arrangements - not what we want here
Oh
Alright
What about the binomial theorem
How would I solve these questions?
have you learnt about the theorem?
then this one is just direct application of binomial theorem, then a bit of tedious expansion
use pascal's triangle to help
I’m not sure how to write something in descending order though
descending order of x is just x^5, x^4, x^3, etc.
The middle term for 211 is 4 right?
you mean 3rd posistion of the terms?
it's to the power of 6 so the middle term would be the 3rd term
I’m blanking on something cause I remember that one term in the binomial Theorem was the number of terms -1
I thought it was the exponent but I guess not
Like this
that's the defenition of a factorial when you do n(n-1)(n-2).....3x2x1
Oh it was R that was -1
What’s the trick with these
My bad for the bad lightning I’ll use the flash on my phone
@tight violet Has your question been resolved?
The question was determine the number of paths from point a to b
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I was able to reduce the equation to (b-6)(a-3) = 18. and then i basically made cases using the idea of factors of 18.
I was able to get the correct answer (6)
But I keep wondering if there is a neater way to do this that does not involve making so many cases, and i also had a raging fear throughout that i'll miss some cases.
Also I spent a couple of minutes making sure that I didnt have a case wherein both the factors are negative. Is there a cleverer way to know that there arent?
All the positive factors of 18 are solutions
The negative solutions you do have to check to see if they are positive or not
so basically as soon as i know the factors of 18, i can tell the number of positive solutions
is this because the coefficient of a and b is 1?
let (a-3)(b-6)=cd
one solution would be a-3=c and b-6=d
so a=c+3 and b=d+6
if c and d are positive integers then a and b are clearly positive
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well any multiple of 4 is non-square-free
well certainly at most 8 cause two of them are divisible by 4
so's any multiple of 9
I would probably brute force with a computer and check whether there is a small example with 8
the one divisible by 9 could be one of those divisible by 4
33-42?
well that was easy
We just said there can't be more than 8
And here's an example with 8
So...
0
Bc you said you can have 10 non-square free consecutive integers
I suppose by crt you can solve a= 0 mod 2^2, a+1=0 mod 3^2, a+2 = 0 mod 5^2, a+3=0 mod 7^2, ...
or is there a nicer solution to that
Yeah that's how I would have done
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can anybody kindly solve this problem?
uh
okay
so $f(x,y)=\frac{(x^2-y^{-2})^x(x-y^{-1})^{y-x}}{(y^2-x^{-2})^y(y+x^{-1})^{x-y}}$
Arnavutköy
we can rewrite $x^2-y^{-2}$ using the difference of squares formula
Arnavutköy
$x^2-y^{-2}=(x+y^{-1})(x-y^{-1})$
Arnavutköy
we can do a similar method for $y^2-x^{-2}$
Arnavutköy
Thus, $f(x,y)=\frac{(x^2-y^{-2})^x(x-y^{-1})^{y-x}}{(y^2-x^{-2})^y(y+x^{-1})^{x-y}}=\frac{(x+y^{-1})^x(x-y^{-1})^x(x-y^{-1})^{y-x}}{(y-x^{-1})^y(y+x^{-1})^y(y+x^{-1})^{x-y}}$
Arnavutköy
combining exponents with the same bases, we get $f(x,y)=\frac{(x+y^{-1})^x(x-y^{-1})^y}{(y-x^{-1})^y(y+x^{-1})^x}$
Arnavutköy
let us rewrite this as $\left(\frac{x+y^{-1}}{y+x^{-1}}\right)^x\left(\frac{x-y^{-1}}{y-x^{-1}}\right)^y$
Arnavutköy
note that $\frac{x+y^{-1}}{y+x^{-1}}=\frac{\frac{xy+1}{y}}{\frac{xy+1}{x}}=\frac{x}{y}$
Arnavutköy
similarly, note that $\frac{x-y^{-1}}{y-x^{-1}}=\frac{x}{y}$
Arnavutköy
Therefore, $f(x,y)=\left(\frac{x}{y}\right)^x\left(\frac{x}{y}\right)^y=\left(\frac{x}{y}\right)^{x+y}$
Arnavutköy
np
Why don't people just use Google?
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@ivory valley Has your question been resolved?
line 2 after "furthermore", what you added in the numerator should cancel out no?
I thought I can still write it because it approaches 0
Before that I tried adding and subtracting terms like x(t0)y(t) but it didn't work out
it should be "that thing" / t-t0 that approaches 0 i think
Since continuity is necessary and x,y are comtinuous that would then make xy continuous as well, So I used that
I basically added -y(t)x'(t0) + y(t0)x'(t0) which exists by assumption and goes to 0
lol
realized
but its $\frac{-y(t)x'(t0) + y(t0)x'(t0)}{t-t_0}$ that you added
bloubbloub
I mean you realized
No
That doesnt make sense, I already considered t-t_0
oh I didn't see the '
So basically I added -x'(t0)(y(t)-y(t0)) so an error term that goes to 0
I think
The way I did it, I was looking what I needed to add and subtract precisely
ok yeah I see
I be home in a bit
I don't see any problems then, since it's very similar to the proof for n=1 anyways
I should have added this I guess
Thank you very much for your time, patience and help! 
.solved
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someone pls explain
the calculator computes arcsin(1/2)
which is actaully 30deg
but arcsin domain is limited to it "cuts" off the other solution at 150deg
but where'd they get the 150?
at 150deg is you draw out the triangle on the unit circle
indeed it has a height of 1/2
as shown on the diagram
hey can someone help me w my algebra
idk how to do it been trying for like an hour and a half
ty
bet
send me the thing
js one of the problems?
ye for now
3 (2x + 2) - 3x = 6 + 3x
alr
i think im js slow
do you have to solve for x
Its okay once you get it it will be very easy
or do you isolate x
i solve for x
ik that because anytime i understand a unit in math i get an a for that unit
no XD
school
its a school work packet my teacher gave us all and it ment for class but im using it to study
You didn’t learn distrubitve law yet?
Yeah it seems weird
wait do you know how to expand
it's basically the same thing
I have the working out
ok.
Uh
um ok
well
this is the woking out:
3(2x+2)-3x=6+3x
=6x+6-3x=6+3x
=3x+6=6+3x
=6=6
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so i have a cubic polyomial, x^3 + 10x^2 - 11x - 180, i am trying to learn the factor theorem,incase i get to do gcse FM, but im wondering how to factorise/solve a cubic, as the equation is very long, and ive heard about trial and erroring roots of the constant but im not sure if that is the most efficient way
so synthetic div is dividing by the root that makes f(x) = 0?
yep
ah kk, ill try that and come back
$$\polylongdiv{x^4 - 3x^2 - 5x + 2}{x + 2}$$
アキラ (>⩊<)
u can do something like this in latex btw
just a sample
oh shit i got very active lol
another sample
$$\polyhornerscheme[x=-2]{x^4 - 3x^2 - 5x + 2}$$
アキラ (>⩊<)
o
w
so uh ive forgotten synthetic div..
ok so did u do something?
nice
so u can make it as x=-5 if ur gonna use synthetic div
but are u sure x+5 works?
I just wanted to add that HOLY that is so cool that you can use the bot to do that, thanks for showing
see
yep
ahhhhh
if it was x+5 that would make it -5 and if x-5 then its 5 🙂
so i put x - 5 outside my division?
for long div?
thats for long div yes
so whats the difference betweeen that and synthetic?
sorry if my english sucks but in long div u could write the x and makes it easier to solve
as for synthetic u could remove the x
oh so synthetic is just -5 divide x^3 + 10x^2 - 11x - 180
also ur english is fine bro
e.g u have x^3 + 10x^2-11x-180 that would make it 1+10-11+180
ohhhh
we are removing x variables here
ohhh so synthetic gets rid of x i seeeee
yep
"sorry if my english sucks" as bro is speaking perfect english
so which is more efficient in an exam scenario?
lol fr
better english than me gng
(and better maths too)
sometimes ppl say it sucks and some of them say its good so i cant disagree with this lol
so i use synthetic?
u can use both
if u always speak like this they might just not be smart enough to understand ur english ig 😭
whatever u think is the best
uhh
its just i speak english bc its the only language they know
o its 00:00 lol perfect a brand new day
lol
i prefer long div
kk can you teach me it then pls..
thankss
let me write it down for u
kk
watchu know about trenbolone vyass
start doing like this
acetate better icl
yea
frfr (i have never touched it im scared)
basically binds to androgen receptors in the muscle cells and acts as synthetic hormone(testosterone) to promost MPS(muscle protien synthesis) which enhances rate at which muscle is gronw
same lol
so uh
wheres the 25 and 2000 come from...
OH ITS AN EXAMPLE
im tapped nvm 😭
so how do i divide x^3 by x for this
think of a small variable that u could subtract it by x^3
so its x^3 - x?
and for 10x^2 as well
not quite
u need to find a variable that makes it x^3 when u multiple so they can go away
oh x^2 and x
x^2 is correct but x isn't 🙂
so u have x^2 and u need to find something that multiples by 10x^2
ohhhhh
its gonna be a number and variable
leave x^2 as its for now bc thats for x^3
i dont even remember the last time i did long division such an ancient skill
lol
we are trying to find 10x^2
10x and x?
wait i think im starting making things complicated for u
😭
eyy congrats on VA!
since we have x+5 as divider i want u to find a number that multiples 5 to get lower number
thanks i got it again after a while
so like 5 and a negative?
5 x [something] = 10
nonono
shit im tripping lol
nanaa all good my brains fried lol but i aint gonna sleep till i understand this lmao
ok here's a thing: what are the two number that gives 5x?
5 and x?
5x and 1 lol
u should watch organic chem tutor video on this
yeaaa
u will leave with 80% confidence with these problems easily
u can use khan academy as well
kk
This video tutorial explains how to perform long division of polynomials with remainder and with missing terms.
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do u get it or still stuck?
uh i mean i understand where the numbers come from now
oh fair
and why long division sucks and calculators should take over lol
not the clankers tho..
now we have x^2+5x
kk
can u continue from this?
where do i write x^2 and 5x
i forgor what do u call this in english
long division?
yes
yeaaa
thats the dividend
just solve it like u are dividing
if u mean the final answer
kk
oh my days im so tapped i wrote the cubic above the line.
thats part of the dividend
Why?
the quotient, i think?
dividend's on the inside
dividend/divisor=quotient
perfect thanks
bc u'd get 25x
huh...
also i'd suggest making negative so u can get rid of it easily after
im kinda lost rn...
i told u i suck at explaining things
but why do we do 5 * 5x and not 5 * 11x or something, and isnt it 5x^2
fair enough
bc -11x is negative
why does the sign matter?
it matters bc u need to cancel them at the end
when the next number comes
for 180
does that makes sense?
bc u found a number to get rid of 10x^2 first
So, that 5x you get, you're multiplying it by the whole divisor, which here is x+5
but its 5x^2?
are we talking abt the very bottom line?
u can continue from here 🙂
Do that, write that product below the 5x^2 -11x and subtract
o shi ty for the bhelp
so i do x^3 + 5x^2 - 0 + 5x^2 - 11x?
So, I would have asked a question before jumping straight into (what this is called is) algebraic long division:
Do you know how to do long division (i.e. with numbers)?
its been a while but yeahh i think so
Make sure you can still do those
drop the remainder down, subtract, bring it to the top, drop down and rinse and repeat
ye
That's what we're doing here as well (but with shitty letters in the mix
)
So here
yeaa
The first bit's a zero, that can piss off 
The rest, 5x^2 - 11x, is the remainder we were doing more rinsing with
do i move the 5x^2 to where the 0 was?
You wouldn't move digits like that in the number variant would you
So we're not doing that here either
So firstly, what product did you get here?
true
so its 5x^2 - 11 *5?
or just the 5x^2
you're getting ahead of yourself
o
thats what all my teachers say...
So remember how you got that yellow term there?
yea i divided x^3 by x
And then that, once you got that, you'd multiply yellow with pink to get orange?
(and then did the subtraction)
this is the rinsing and repeating we've got to
wait wym yello * pink
The yellow and pink things I've highlighted
Same thing again at this stage - except here, it's blue times pink, to get purple
you do x ^ 2 * x to get the x^3 and the x * x^2 to get 5x^2
yeeeee
(essentially we're looking at the big terms to find what to put on the top, and then multiplying this with the whole divisor just to fine-tune and get a new division to check)
kk
yeee
careful
yea -11 - (+25) = 14
Not quite
Think number-line tactics - minus means left, plus means right
You go left 11, then left 25
Which makes?
36...
In which direction?
negative sir...
nah igu lol
especially when i forgot my negatives
ahh kk so(lemme get a pic)
If you had a
9
4
5
(one way I avoid this hassle, btw, is thinking "Okay, so I've written down this +25x; what would I need to add to this to get -11x?")
uh
[this works for me, it may work for you, give it a try and see what works]
Back to this tho - now bring down that -180
-36x - 180, but yh
yeaa
wait dafuq how did I not catch that
we just said this is a minus lmao
my signs are
not my strong suit...
yeahh memory of a goldfish im tellling you.. 😭
Practise number line stuff as well then 
if maths had no signs itd be sound
dw, it might be basic shit, but that shit's important 🫡
yeahhhh thats true af lmao
It's never a bad idea to strengthen your arithmetic skills
Onwards then - the "big" term there is that -36x
do i revise trig or do the arithmatic on sparx? i always do the trig 😭
yea
("big", as in it's the one with the higher x-power)
so im guessing / by x?
x divides -36x how many times?
once
uhhh not quite?
shit. im embarrasing myself here lmao
Alternatively phrased, how many multiples of x make -36x?
This might just be a phrasing thing dw
😭
Not **+**36
-36
yeee
i keep forgetting those damn signs lmao
yea did that
Multiply this blue by pink to get the green bit
yee
WOAH WHAT
You've written the -36 in there
So the whole quotient (result) is x^2 + 5x -36
that bit's part of the answer too
(even if it cancels, if it's the last step, write down the 0 you get under the yellow line - so it's clear there's no remainder)
so i write x^2 + 5x - 36 up top
ye
and then 36x +180 at bottom
where the green bit is, yh
so that cancels to 0
ye
btw, this didn't work anyways lol - A^2 + 2B doesn't equal (A + B)(A + B); I think you got confused with difference-of-two-squares 
Yeaaa
Hmmm
So its x -9 x + 4
X = -9*
X = 4*
ye
So check this again then
We'd begun with a cubic
So would it have worked if i do cubic formula
Well the third factor was the thing we were dividing by, wasn't it
ahhhhhh
Not +5
-5
This?
What formula do you have?
fyi there are a few
(related: read about Nicolo Tartaglia https://en.wikipedia.org/wiki/Nicolo_Tartaglia#Solution_to_cubic_equations - not because of the maths but because it's comical lol)
Nicolo, known as Tartaglia (Italian: [tarˈtaʎʎa]; 1499/1500 – 13 December 1557), was an Italian mathematician, engineer (designing fortifications), a surveyor (of topography, seeking the best means of defense or offense) and a bookkeeper from the then Republic of Venice. He published many books, including the first Italian translations of A...
My guess is you mean this one?
Lmao bro saw his work “ by accident”
Yhhhh
Right, so what you gotta do here is steal the equation's antidepressants manipulate the cubic in such a way that it resembles the first equation here
Now, the actual method to do that is not really that obvious
Let's see if I can't find a good explanation somewhere...
I mean your making it t^3 +pt +q.
oki
Hiw hard is that
(yee - so if there's no squared term, that's easy - but if there is one, it's not as clear-cut)
multiply by x…
(this is where I look through my uni notes to see if I might find something
)
I've stumbled across these notes https://people.math.osu.edu/derdzinski.1/courses/4552/4552-cubic-quartic.pdf btw - not mine
lol
This being the search term
lmao yk its tuff when it starts with “math 4552”
yh, dw too much about it, it's rather a lot for someone not used to seeing tons of algebra lol
4552 is just a module code lol
Yeaa i mean i prefer algebra lmao
Like what AQA and Edexcel do with their exams tho
It's semi-random
There's no "this is 0001, this is 0002, etc"
Ohhhhh
this is a weird way to present Cardano's formula, but it's pretty useful for computation
If it's not clear - find Q and R first; then S and T
Then x_1, x_2 and x_3 are your solutions
So why have they put different equations for s
for s?
Yhh
This is the not-at-all-obvious trick to get rid of this substitution
So the replacing thing confused me
So we can get them with 3 equations
(not unlike taking the plus or minus from the quadratic)
Well I'm reading off of https://proofwiki.org/wiki/Cardano's_Formula for this
But this is doing a similar proof
K
To briefly explain, because I agree this is so not clear lol
It's ridiculously good
Suppose there z were a solution
Further, I'm gonna call a new variable w, so defined up there in that image
How do they get the equation for the roots? Do they js make it up or sum
Kk
If I then rearrange that w-definition to make z the subject, and then plug this into the cubic and simplify, I end up with no w^2 term
I've stolen the cubic's antidepressants turned this into a depressed cubic
Now it turns out we've known solutions to these for centuries
O
[but, as that Tartaglia story explains, because mathy bois were so busy boasting about who had the bigger formula. they didn't want to share it]
Given the character being yeeted here is also called Tartaglia, this is an accurate depiction of what these were like
Lmaoo
😭😭🤣🤣
So its js rearranging in a nutshell
ye
Ahhhh i see
The rest of that PDF involves making some more snarky substitutions to get some nifty formulas
yea ill have a proper look in the morning lol
Maths on energy drinks surely breaks laws somewhere
This one might be a little easier to digest
The reason these are uni-level explanations at all btw is to do with the context they're in
kk
wym?
Namely - there is a quadratic formula (you learn this in school)
There also happens to be a cubic formula (which is messy to get to, but it exists)
There is a quartic one yh
That PDF covers it right after that cubic one
Havent we been talkin bout the cubic one?
Ahhhh
I see
after this sorry excuse for a line lol
k
Yea i cant even understand those letters
Ik the set one
I think
yh they explain these along the way, but it's pretty weird to immediately apply this
truuu
ProofWiki's is easier to use as a tool
Now, the question is - does this generalise?
Wym by that
Like generalize
Is there a formula for any polynomial?
Uh
This
O thats a question
A good one
If there was
That would be useful
So like if highest power = z: use this and etc
Well, it turns out that, in the 1800s, a whole field called Galois Theory was built upon the proof that "lol no there's no quintic one fok you hahahah"
ye
I'll briefly explain, suffice to say that except for maybe Further Maths AL FP2 students this is certainly beyond the scope lol
We can talk about the collection of polynomials (under certain conditions, e.g. "its coefficients are real") as some object called a ring
Ahh
Lol
k
Galois Theory explores whether these rings can be compared to some associated "group" (groups are another maths-y object, and this is the FP2 thing)
So a group is a lot of rings?
No, rings and groups are different objects
Silly tho it is
You can probably Wiki them if you want for more
The important thing about groups for this discussion is that they may or may not have a property called "soluable"/"solvable"
[the spelling difference is because the old pricks can't write v properly. but the shit stuck to the fan so here we are with two words]
Lmaoo
It turns out, from the Theory, that the question "Does a polynomial ring with certain conditions have solutions we can just compute? (i.e. is there a formula?)" is mathematically equivalent to "Is the associated group solvable?"
K
(we call the associated group the Galois group of that ring)
So: "The ring of quintic polynomials has a formula for their solutions" is equivalent to "The Galois group of this ring is solvable"
Kk
That last statement - we've proved some-the-
-how - is false
So actually there's no quintic formula
(thus by extension there's no sextic or septic equations etc. (yes those are actual words wtf is this language even))
So because the ring past quartic doesn’t have the solvable propery?
That of the quadratics is, for instance, which is why there's a quadratic formula
kk
The Galois group of the ring of quintic polynomials isn't solvable (eugh that's a lot to type)
so its quartic then quintic
Ahhhh
Anyways there you go, a shitty crash course on a third-year UG maths module 
Lmao much appreciated
W crash course
Awesome and tnaks for the help with the cubics aswll
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Hi, I just have a question about a step taken in a worked solution for an initial value problem
In the last line he does the partial fraction decomposition, but I am lost with what steps he took
From what I can tell, the constant A on the LHS is pi^2/4, and on the RHS B is 1 and C is s
s²+pi²/4 -s² in numerator
Here is the problem btw
huh? xD
oh right
why is pi^2/4 used in the numerator pls?
I assume this is to make the decomposition work out nicely but idk how this was decided
In a similar problem, the partial fraction decomposition is for the same denominator, what I am confused on is why the numerator of the fraction that is to be separated is not considered in the partial fraction decomposition
this is dumb question im sry lol
It is not a dumb question
And i m not sure how they got thaat either
My approach would be to decompose this
but instead he replaces numerator with the pi^2 term and this is somehow equal to the term being decomposed 😅
(Do you happen to have what comes after the representing part? My guess is that for that second third term, they plan to multiply and divide by pi/4 4 to make things nicer to work with, maybe?)
(re this, and...
...this
)
I will send them now 1 sec
I am doing the partial fraction decomp long hand to see if his result is indeed equal when 2pi^2*exp(5s) is used instead of pi^2/4
Ah accidentally read the wrong one, but basically I think they just multiplied/divided the third term by 4 (which is how you get the factor of 8 here, 2 = 8/4)
just done, will send my values for the decomp here
I am mainly hung up on why he did not decompose directly like this
sry if this is very basic stuff, I am pretty lost in this topic
Probably to save having to show you the work, also with some of these, you can, with enough experience, see how to decompose them without actually doing all the hard work [of writing out the form and finding the coefficients] (as suggested here
)
(also, as a side note, that second numerator should be in the form Bs + C, the degree of the numerator being one less than that of the denominator
)
what does that mean 😭
Hence 
do you by chance know where I can read up on this? it is not mentioned in lecture notes
Yea, try out the work again, but take the decomposition to be $\frac{A}s + \frac{Bs + C}{s^2 + \frac{\pi^2}4}$
@woeful trench
And lemme see if I can find something for you 
e.g. like this one here (which is more clearly explained by their example than by the screenshot
)
Or this one, which is slightly better 
omg
thank you man
😭
so what I did was rubbish
this makes sense
Imma do it again
Yep you should see it works out if you do it that way 
@lavish mortar Has your question been resolved?
made mistake with first attempt will close in like 10 min
I did it but didnt factor exp(-5s) back in
A and B aren't nonsense now at least
sry to bug you again on this, I just really want to understand what the correct approach is for this specific step of laplace IVP
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got it, I made a stupid
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Hello, Rational Inequalities.
(2x/(x-4))≥1
Hello i have returned from a quiz @toxic ridge
i checked out the wavy curve thing and I still dont understand it
What'd your question on that?
how to do the number graph
What's a number graph?
Oh
lik ds
So you are basically asking for the solution?
Okay
how to know the intervals ig
Well, in order to attain them you would need to solve this inequality, which would require two cases
(x+4)/(x-4)≥0 i got ts
Another approach is the following:
[\f{2x}{x-4}-1 = \f{2x-(x-4)}{x-4} \ge 0 ]
Now you need to see when \textbf{both} the numerator and denominator are positive.
yez i got (x+4)/(x-4)≥0
Ok nice
