#help-4

1 messages · Page 32 of 1

stark wedge
#

when you write 3¼ do you mean three plus a quarter? or do you mean 3 raised to the power of 1/4?

fossil torrent
#

What do you mean by Newton's formula?

stark wedge
#

$x^2 - 3^{1/4} x + 3^{1/2}=0$

rocky lotusBOT
stark wedge
#

like this?

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was unclear from your original msg

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you can find the roots as complex numbers and then convert them into polar form.

frozen laurel
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Oh wait

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I did something

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I think I got the answer

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I played around with it

fossil torrent
#

In your original question as you posed it, the sign of the 3^(1/4) was negative

vale dockBOT
#

@frozen laurel Has your question been resolved?

vale dockBOT
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sharp cloud
#

Hi I need help

vale dockBOT
sharp cloud
#

I need help from 1. to 3., I have zero knowledge about it but yeah

wraith heart
#

,rotate

#

pain

hearty belfry
#

😭

rocky lotusBOT
wraith heart
#

use pythagorean theorem

hearty belfry
sharp cloud
stark wedge
#

before we get to pythagoras we need to also find out how to identify the right angle in each triangle

sharp cloud
#

,rcw

#

pain

hearty belfry
rocky lotusBOT
sharp cloud
#

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

stark wedge
#

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

sharp cloud
#

so EG = 4^2 + 3^2

stark wedge
#

EG**^2** = 4^2 + 3^2.

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in pythagoras' theorem, all sides are squared.

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you shouldn't omit the square on any of them. it's a pretty common stumbling spot.

sharp cloud
#

How about for BE?

stark wedge
#

look at triangle BGE, which is again a right triangle with the right angle sitting at G

sharp cloud
#

oh actually

stark wedge
#

and now its two known sides are EG (which we just found) and BG (which is the length, 12)

sharp cloud
#

its a right angle?

stark wedge
#

yes

#

imagine tipping the cuboid over so that face EFGH rests on the ground

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then edge BG will be upright and thus perpendicular to anything that's level with the ground

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incl. edge EG

sharp cloud
#

ohhh so the answer is 13

#

can you help with no. 3?

stark wedge
#

sure, do you know the SOH-CAH-TOA mnemonic?

sharp cloud
#

yeah?

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sin = opp/hyp, cos = adj/hyp, tan = opp/adj?

stark wedge
#

yes.

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it's just this mnemonic and figuring out what goes where.

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carefully mark all known side lengths and right angles in every triangle involved.

sharp cloud
#

could I ask for help on no. 2, b.?

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uh length of BF to be exact

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bcs I got 12.64

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could I ask help double checking? Cs I think it's wrong

turbid valve
#

[your pen's kinda blocking the diagram]

turbid valve
#

But I got root(160) too, which is 12 point something yh

vale dockBOT
#

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cosmic crest
#

need to find error bound on an approximation from simpson's rule.

cosmic crest
#

(delta X ^ 4)/180 all that multiplied by (b-a) times K

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,calc ((1/4)^4)/180

rocky lotusBOT
#

Result:

2.1701388888889e-5
cosmic crest
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,calc 2.1701388888889e-5 * 3

rocky lotusBOT
#

Result:

6.5104166666667e-5
cosmic crest
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K * 6.5104166666667e-5

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need to solve for K

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iirc I need to find the max value of K within the given interval which is [1,4]

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and choose K to be that

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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?

rocky lotusBOT
#

Result:

0.0015625
cosmic crest
#

,calc 6.5104166666667e-5 * 24

rocky lotusBOT
#

Result:

0.0015625
wraith heart
#

!original

vale dockBOT
#

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.

cosmic crest
# wraith heart !original

integral from 1 to 4 x^4 dx. a. find sympsons rule approximation. b. find error bound on your approximation

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I suppose I shouldn't have even included this context

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my question is how can I find the max point on the given interval for x^4

wraith heart
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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

cosmic crest
#

(I know we need fourth derivative here and the max is 24=K but I wanna know how to solve harder problems without graphing)

wraith heart
cosmic crest
#

omg yeahhh the 1st deriv test

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okay bet that's all I needed, tysm

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.close

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#
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rocky lotusBOT
#

brandon

vale dockBOT
#

@tawdry lintel Has your question been resolved?

vale dockBOT
#

@tawdry lintel Has your question been resolved?

vale dockBOT
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@tawdry lintel Has your question been resolved?

vale dockBOT
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@tawdry lintel Has your question been resolved?

charred burrow
#

<@&286206848099549185>

vale dockBOT
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@tawdry lintel Has your question been resolved?

leaden kraken
#

what is the way you use?

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tight violet
#

I need a reminder on how to do these questions cause I forgot

tight violet
#

I forgot how they work I need an explanation on them to jog my memory

hearty belfry
#

which just means n choose r

tight violet
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Like if theres 12 teachers you can choose between 7

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So 12c7

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Is that right?

hearty belfry
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yep joia

tight violet
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Cause in some questions it becomes like

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12!/7!

hearty belfry
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although 12!/7! is the wrong option

tight violet
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The formula isn’t what I’m concerned about

tight violet
tight violet
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Let me find one rq

hearty belfry
#

alright

tight violet
hearty belfry
# tight violet

the wording is a bit confusing but I think it's just another nCr question but you have duplicates for R?

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also Darren not knowing how to spell his name is funny to me opencry

tight violet
hearty belfry
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like the question says they already had the letter D being in front

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so D is excluded

tight violet
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I get it’s cause of the duplicate r but why do we divide and not subtract or smth

tawny moon
#

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

tight violet
#

Alright

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What about the binomial theorem

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How would I solve these questions?

tawny moon
#

have you learnt about the theorem?

tight violet
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Yeah

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It was like 2 months ago so I’m blanking on it a little

tawny moon
#

then this one is just direct application of binomial theorem, then a bit of tedious expansion

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use pascal's triangle to help

tight violet
#

I’m not sure how to write something in descending order though

tawny moon
#

descending order of x is just x^5, x^4, x^3, etc.

tight violet
hearty belfry
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it's to the power of 6 so the middle term would be the 3rd term

tight violet
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I thought it was the exponent but I guess not

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Like this

hearty belfry
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that's the defenition of a factorial when you do n(n-1)(n-2).....3x2x1

tight violet
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Oh it was R that was -1

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What’s the trick with these

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My bad for the bad lightning I’ll use the flash on my phone

vale dockBOT
#

@tight violet Has your question been resolved?

tight violet
# tight violet

The question was determine the number of paths from point a to b

vale dockBOT
#

@tight violet Has your question been resolved?

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midnight pier
#

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?

lament copper
#

All the positive factors of 18 are solutions

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The negative solutions you do have to check to see if they are positive or not

midnight pier
#

so basically as soon as i know the factors of 18, i can tell the number of positive solutions

midnight pier
lament copper
#

let (a-3)(b-6)=cd

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one solution would be a-3=c and b-6=d

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so a=c+3 and b=d+6

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if c and d are positive integers then a and b are clearly positive

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#

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stark wedge
#

well any multiple of 4 is non-square-free

ebon glade
#

well certainly at most 8 cause two of them are divisible by 4

stark wedge
#

so's any multiple of 9

ebon glade
#

I would probably brute force with a computer and check whether there is a small example with 8

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the one divisible by 9 could be one of those divisible by 4

ruby sleet
#

33-42?

ebon glade
#

well that was easy

ruby sleet
#

We just said there can't be more than 8

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And here's an example with 8

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So...

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0

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Bc you said you can have 10 non-square free consecutive integers

ebon glade
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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

ruby sleet
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prime shore
#

can anybody kindly solve this problem?

magic lynx
#

uh

#

okay

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so $f(x,y)=\frac{(x^2-y^{-2})^x(x-y^{-1})^{y-x}}{(y^2-x^{-2})^y(y+x^{-1})^{x-y}}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

we can rewrite $x^2-y^{-2}$ using the difference of squares formula

rocky lotusBOT
#

Arnavutköy

magic lynx
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$x^2-y^{-2}=(x+y^{-1})(x-y^{-1})$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

we can do a similar method for $y^2-x^{-2}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

Thus, $f(x,y)=\frac{(x^2-y^{-2})^x(x-y^{-1})^{y-x}}{(y^2-x^{-2})^y(y+x^{-1})^{x-y}}=\frac{(x+y^{-1})^x(x-y^{-1})^x(x-y^{-1})^{y-x}}{(y-x^{-1})^y(y+x^{-1})^y(y+x^{-1})^{x-y}}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

combining exponents with the same bases, we get $f(x,y)=\frac{(x+y^{-1})^x(x-y^{-1})^y}{(y-x^{-1})^y(y+x^{-1})^x}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

let us rewrite this as $\left(\frac{x+y^{-1}}{y+x^{-1}}\right)^x\left(\frac{x-y^{-1}}{y-x^{-1}}\right)^y$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

note that $\frac{x+y^{-1}}{y+x^{-1}}=\frac{\frac{xy+1}{y}}{\frac{xy+1}{x}}=\frac{x}{y}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

similarly, note that $\frac{x-y^{-1}}{y-x^{-1}}=\frac{x}{y}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

Therefore, $f(x,y)=\left(\frac{x}{y}\right)^x\left(\frac{x}{y}\right)^y=\left(\frac{x}{y}\right)^{x+y}$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

does that make sense?

#

@prime shore

prime shore
#

it does!

#

thanks for helpingg i spent a lot of time pondering over how to solve this

magic lynx
#

np

fossil pelican
#

Why don't people just use Google?

vale dockBOT
#

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ivory valley
vale dockBOT
ivory valley
#

Is it correct?

#

Should have stated R^n -> R

vale dockBOT
#

@ivory valley Has your question been resolved?

light saddle
#

line 2 after "furthermore", what you added in the numerator should cancel out no?

ivory valley
#

I thought I can still write it because it approaches 0

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Before that I tried adding and subtracting terms like x(t0)y(t) but it didn't work out

light saddle
#

it should be "that thing" / t-t0 that approaches 0 i think

ivory valley
#

Since continuity is necessary and x,y are comtinuous that would then make xy continuous as well, So I used that

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I basically added -y(t)x'(t0) + y(t0)x'(t0) which exists by assumption and goes to 0

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lol

#

realized

light saddle
#

but its $\frac{-y(t)x'(t0) + y(t0)x'(t0)}{t-t_0}$ that you added

rocky lotusBOT
#

bloubbloub

light saddle
#

I mean you realized

ivory valley
#

No

ivory valley
light saddle
#

oh I didn't see the '

ivory valley
#

So basically I added -x'(t0)(y(t)-y(t0)) so an error term that goes to 0

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I think

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The way I did it, I was looking what I needed to add and subtract precisely

light saddle
#

ok yeah I see

ivory valley
#

I be home in a bit

light saddle
#

I don't see any problems then, since it's very similar to the proof for n=1 anyways

rocky lotusBOT
ivory valley
#

I should have added this I guess

ivory valley
#

.solved

vale dockBOT
#
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grizzled furnace
vale dockBOT
grizzled furnace
#

someone pls explain

fickle rose
#

the calculator computes arcsin(1/2)

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which is actaully 30deg

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but arcsin domain is limited to it "cuts" off the other solution at 150deg

grizzled furnace
#

but where'd they get the 150?

fickle rose
#

at 150deg is you draw out the triangle on the unit circle

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indeed it has a height of 1/2

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as shown on the diagram

hexed basin
#

hey can someone help me w my algebra

hexed basin
#

idk how to do it been trying for like an hour and a half

hexed basin
grizzled furnace
hexed basin
#

ty

#

its js that i dont understand the concept or procces

grizzled furnace
#

send me the thing

hexed basin
#

js one of the problems?

grizzled furnace
#

ye for now

hexed basin
#

3 (2x + 2) - 3x = 6 + 3x

grizzled furnace
#

alr

hexed basin
#

i think im js slow

grizzled furnace
#

do you have to solve for x

hexed basin
#

yea

#

btw heads up im a little dumb so when u explain it js pls make it simple 🙏

pliant sonnet
grizzled furnace
#

or do you isolate x

hexed basin
#

i solve for x

hexed basin
grizzled furnace
#

alr

#

so

#

yk the distrubitive law?

hexed basin
#

no XD

grizzled furnace
#

oh ok

#

where'd you get this quesion?

hexed basin
#

school

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its a school work packet my teacher gave us all and it ment for class but im using it to study

pliant sonnet
#

You didn’t learn distrubitve law yet?

lyric sundial
#

Yeah it seems weird

grizzled furnace
#

wait do you know how to expand

#

it's basically the same thing

#

I have the working out

hexed basin
#

ion jack

#

havent payed attention in forever in math

grizzled furnace
#

ok.

pliant sonnet
#

Uh

grizzled furnace
#

um ok

#

well

#

this is the woking out:

#

3(2x+2)-3x=6+3x

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=6x+6-3x=6+3x

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=3x+6=6+3x

#

=6=6

vale dockBOT
#

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grizzled furnace
#

.close

vale dockBOT
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midnight pier
#

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

oak crane
#

u need to find possible numbers

#

so u can use long div or synthetic div

midnight pier
#

so synthetic div is dividing by the root that makes f(x) = 0?

oak crane
#

yep

midnight pier
#

ah kk, ill try that and come back

oak crane
#

$$\polylongdiv{x^4 - 3x^2 - 5x + 2}{x + 2}$$

rocky lotusBOT
#

アキラ (>⩊<)

oak crane
#

u can do something like this in latex btw

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just a sample

#

oh shit i got very active lol

oak crane
#

$$\polyhornerscheme[x=-2]{x^4 - 3x^2 - 5x + 2}$$

rocky lotusBOT
#

アキラ (>⩊<)

oak crane
#

🙂

#

i personally like long div bc its easier and faster

midnight pier
midnight pier
midnight pier
oak crane
#

thats ok

#

i can help u

midnight pier
#

cus in my school for the normal igcse its calc only sooo

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YES pls

oak crane
#

ok so did u do something?

midnight pier
#

so i have x + 5 root x^3 + 10x^2 - 11x -180

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right now

oak crane
#

nice

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so u can make it as x=-5 if ur gonna use synthetic div

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but are u sure x+5 works?

midnight pier
#

i thought we take the inverse of f(x)

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its x - 5 that works

light saddle
#

I just wanted to add that HOLY that is so cool that you can use the bot to do that, thanks for showing

oak crane
#

,w (-5)^3 + 10(-5)^2 - 11(-5) - 180 =

oak crane
#

see

midnight pier
#

OHHHH so if -5 works that means f(x) = f(5)?

#

and the factor becomes x + 5

oak crane
#

yep

midnight pier
#

ahhhhh

oak crane
#

if it was x+5 that would make it -5 and if x-5 then its 5 🙂

midnight pier
#

so i put x - 5 outside my division?

oak crane
#

for long div?

midnight pier
#

synthetic

#

or is it same

oak crane
#

for synthetic write it as -5

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bc x+5

midnight pier
#

ahhh kk

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so it becomes x+5 divide x^3 + 10x^2 - 11x - 180

oak crane
#

thats for long div yes

midnight pier
#

so whats the difference betweeen that and synthetic?

oak crane
#

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

midnight pier
#

oh so synthetic is just -5 divide x^3 + 10x^2 - 11x - 180

#

also ur english is fine bro

oak crane
midnight pier
#

ohhhh

oak crane
#

we are removing x variables here

midnight pier
#

ohhh so synthetic gets rid of x i seeeee

oak crane
#

yep

quiet tide
#

"sorry if my english sucks" as bro is speaking perfect english

midnight pier
#

so which is more efficient in an exam scenario?

midnight pier
#

better english than me gng

#

(and better maths too)

oak crane
midnight pier
#

so i use synthetic?

oak crane
#

u can use both

quiet tide
oak crane
#

whatever u think is the best

midnight pier
#

uhh

oak crane
midnight pier
#

o its 00:00 lol perfect a brand new day

oak crane
#

lol

midnight pier
#

but anyway

#

uh

#

which would you prefer

oak crane
#

i prefer long div

midnight pier
#

kk can you teach me it then pls..

oak crane
#

yea sure

midnight pier
#

thankss

oak crane
#

let me write it down for u

midnight pier
#

kk

quiet tide
#

watchu know about trenbolone vyass

midnight pier
#

OOO

#

AIGHT

#

TRENOBOLONE ACETATE AND ENTHATE

oak crane
#

start doing like this

midnight pier
#

acetate better icl

midnight pier
quiet tide
oak crane
#

u need to divide it just like u are dividing 25/2000

#

just an example

midnight pier
midnight pier
midnight pier
#

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

oak crane
#

think of a small variable that u could subtract it by x^3

midnight pier
#

so its x^3 - x?

oak crane
#

and for 10x^2 as well

oak crane
midnight pier
#

o

#

do i divide it?

#

to give x^2?

oak crane
#

u need to find a variable that makes it x^3 when u multiple so they can go away

midnight pier
#

oh x^2 and x

oak crane
#

x^2 is correct but x isn't 🙂

midnight pier
#

O

#

uh

#

x^1...

oak crane
#

so u have x^2 and u need to find something that multiples by 10x^2

midnight pier
#

ohhhhh

oak crane
#

its gonna be a number and variable

midnight pier
#

so x^2 * something = 10x^2

#

so itll be 10

oak crane
#

leave x^2 as its for now bc thats for x^3

quiet tide
#

i dont even remember the last time i did long division such an ancient skill

midnight pier
#

lol

oak crane
#

we are trying to find 10x^2

midnight pier
#

10 and x^2

oak crane
#

nope

#

try again

midnight pier
#

10x and x?

oak crane
#

not quite 😭

#

think of a small number

midnight pier
#

erm

#

5x and 2x..

oak crane
#

wait i think im starting making things complicated for u

midnight pier
#

😭

final adder
oak crane
#

since we have x+5 as divider i want u to find a number that multiples 5 to get lower number

oak crane
oak crane
midnight pier
#

OH, 5x(2) = 10x..

#

or is it not 10x

oak crane
#

nonono

midnight pier
#

shit im tripping lol

oak crane
#

sorry i suck at explaining things 😭

#

how i can give u a hint

midnight pier
#

nanaa all good my brains fried lol but i aint gonna sleep till i understand this lmao

oak crane
#

ok here's a thing: what are the two number that gives 5x?

quiet tide
#

no 2 numbers give 5x

#

unless u mean just 5 and x

midnight pier
#

5 and x?

oak crane
#

5x and 1 lol

midnight pier
#

OHHH

#

SHIT

quiet tide
#

u should watch organic chem tutor video on this

midnight pier
#

yeaaa

quiet tide
#

u will leave with 80% confidence with these problems easily

midnight pier
#

oo

#

might do tbf

oak crane
#

u can use khan academy as well

midnight pier
#

kk

quiet tide
oak crane
midnight pier
oak crane
#

oh fair

midnight pier
#

and why long division sucks and calculators should take over lol

#

not the clankers tho..

oak crane
#

now we have x^2+5x

midnight pier
#

kk

oak crane
#

can u continue from this?

midnight pier
#

where do i write x^2 and 5x

oak crane
#

i forgor what do u call this in english

midnight pier
#

long division?

oak crane
#

yes

midnight pier
#

yeaaa

quiet tide
#

thats the dividend

oak crane
#

just solve it like u are dividing

quiet tide
#

if u mean the final answer

midnight pier
#

kk

oak crane
#

i forgor what do u call this lol

midnight pier
#

oh my days im so tapped i wrote the cubic above the line.

quiet tide
#

thats part of the dividend

midnight pier
#

Ok i have this

#

Do i multiply 11x by x?

oak crane
#

nope

#

multiple it by 5x

midnight pier
#

Why?

final adder
#

dividend's on the inside

#

dividend/divisor=quotient

oak crane
#

perfect thanks

oak crane
midnight pier
#

huh...

oak crane
#

also i'd suggest making negative so u can get rid of it easily after

midnight pier
#

im kinda lost rn...

oak crane
#

gives 25x

oak crane
midnight pier
#

but why do we do 5 * 5x and not 5 * 11x or something, and isnt it 5x^2

midnight pier
midnight pier
#

why does the sign matter?

oak crane
#

it matters bc u need to cancel them at the end

#

when the next number comes

#

for 180

#

does that makes sense?

midnight pier
#

yea kinda

#

but then why do you multiply the 5 with 5x and not 5x^2

oak crane
#

bc u found a number to get rid of 10x^2 first

turbid valve
midnight pier
#

but its 5x^2?

midnight pier
turbid valve
midnight pier
midnight pier
turbid valve
#

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)?

midnight pier
#

its been a while but yeahh i think so

turbid valve
#

Make sure you can still do those

midnight pier
#

drop the remainder down, subtract, bring it to the top, drop down and rinse and repeat

turbid valve
#

ye

#

That's what we're doing here as well (but with shitty letters in the mix opencry)

#

So here

midnight pier
#

yeaa

turbid valve
#

The first bit's a zero, that can piss off KEK

midnight pier
#

o yea

#

lol i forgot

turbid valve
#

The rest, 5x^2 - 11x, is the remainder we were doing more rinsing with

midnight pier
#

do i move the 5x^2 to where the 0 was?

turbid valve
#

So we're not doing that here either

turbid valve
midnight pier
#

or just the 5x^2

turbid valve
#

you're getting ahead of yourself

midnight pier
#

o

midnight pier
turbid valve
#

So remember how you got that yellow term there?

midnight pier
#

yea i divided x^3 by x

turbid valve
#

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

midnight pier
#

wait wym yello * pink

turbid valve
midnight pier
#

ye

#

OHHHH

#

i seeee

turbid valve
#

Same thing again at this stage - except here, it's blue times pink, to get purple

midnight pier
#

you do x ^ 2 * x to get the x^3 and the x * x^2 to get 5x^2

midnight pier
#

so 5 * x + 5

#

5x^2 + 25x

turbid valve
#

(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)

midnight pier
#

kk

turbid valve
midnight pier
#

ahhhh

#

lemme write dis

#

and subtract to get 14x

turbid valve
#

careful

midnight pier
#

and then bring it up

#

O

turbid valve
#

You've got a -11 up top

#

And a +25 below

#

You want to subtract -11 by +25

midnight pier
#

yea -11 - (+25) = 14

turbid valve
#

...you sure?

#

expand that bracket out?

midnight pier
#

ah shit

#

its -14 isnt it.

turbid valve
#

Not quite

midnight pier
#

like -11 - 25 i mea

#

n

turbid valve
#

Think number-line tactics - minus means left, plus means right

#

You go left 11, then left 25

#

Which makes?

midnight pier
#

36...

turbid valve
#

In which direction?

midnight pier
#

negative sir...

turbid valve
#

ye

#

(no need to call me sir lol)

#

So -11 - 25 is?

midnight pier
#

lmao its habit i call teachers sir lmao

#

-36...

turbid valve
midnight pier
#

especially when i forgot my negatives

midnight pier
#

so where do i put -36x? is it next to the 5x?

turbid valve
#

below the
-11x
+25x


[HERE]

#

Same with numbers

midnight pier
#

ahh kk so(lemme get a pic)

turbid valve
#

If you had a
9
4


5

midnight pier
turbid valve
#

(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?")

midnight pier
#

uh

turbid valve
#

[this works for me, it may work for you, give it a try and see what works]

turbid valve
midnight pier
#

so 36 - 180

turbid valve
#

-36x - 180, but yh

midnight pier
#

yeaa

turbid valve
midnight pier
#

OOPS SHIT

#

uh

turbid valve
midnight pier
#

my signs are

#

not my strong suit...

#

yeahh memory of a goldfish im tellling you.. 😭

turbid valve
#

Practise number line stuff as well then opencry

midnight pier
#

if maths had no signs itd be sound

turbid valve
#

dw, it might be basic shit, but that shit's important 🫡

midnight pier
turbid valve
#

It's never a bad idea to strengthen your arithmetic skills

midnight pier
#

yep thats true

#

i js keep putting it off lmao

#

like i always think

turbid valve
midnight pier
#

do i revise trig or do the arithmatic on sparx? i always do the trig 😭

turbid valve
#

("big", as in it's the one with the higher x-power)

midnight pier
#

so im guessing / by x?

turbid valve
#

ye

#

Essentially, how many time does the x (from x+5) divide -36x?

midnight pier
#

ahhh so = -36-180

#

O

#

nvm

#

uh

#

7

#

wait

#

no

#

1

turbid valve
#

x divides -36x how many times?

midnight pier
#

once

turbid valve
#

uhhh not quite?

midnight pier
#

shit. im embarrasing myself here lmao

turbid valve
#

Alternatively phrased, how many multiples of x make -36x?

midnight pier
#

AH

#

36

turbid valve
#

This might just be a phrasing thing dw

midnight pier
#

😭

turbid valve
#

Not **+**36

midnight pier
#

-36

turbid valve
#

yeee

midnight pier
#

i keep forgetting those damn signs lmao

turbid valve
#

-36 up top

#

Repeat the process

midnight pier
#

so i divide -180 by 5

#

so that is

#

-36

turbid valve
#

So write -36 in the blue bit

midnight pier
#

yea did that

turbid valve
#

Multiply this blue by pink to get the green bit

midnight pier
#

so 36 * x = 36x and 36 * 5 = 180

#

so that cancels

#

OH

turbid valve
#

yee

midnight pier
#

ITS JUST X^2 + 5X

#

WHICH FACTORISES TO

turbid valve
midnight pier
#

(X+2.5)(X+2.5)

#

ah shit

#

wat have i done..

turbid valve
#

So the whole quotient (result) is x^2 + 5x -36

#

that bit's part of the answer too

turbid valve
# midnight pier so that cancels

(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)

midnight pier
#

so i write x^2 + 5x - 36 up top

turbid valve
#

ye

midnight pier
#

and then 36x +180 at bottom

turbid valve
#

where the green bit is, yh

midnight pier
#

so that cancels to 0

turbid valve
#

ye

midnight pier
#

then do i factorise

#

x^2 + 5x - 36

turbid valve
#

YEE

#

(and this does factorise nicely, thank fok opencry )

midnight pier
#

lmaoo

#

Uh

#

So lets see what multiplies to 36 adds to 5

turbid valve
# midnight pier (X+2.5)(X+2.5)

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 KEK

midnight pier
#

Hmmm

#

So its x -9 x + 4

#

X = -9*

#

X = 4*

turbid valve
#

ye

midnight pier
#

AHHHHH

#

So thats the anseer

#

And how to divide cubics

turbid valve
#

We'd begun with a cubic

midnight pier
#

So would it have worked if i do cubic formula

midnight pier
#

Ah fuck

#

Its jot over is it..

turbid valve
#

Well the third factor was the thing we were dividing by, wasn't it

midnight pier
#

OH

#

So 5,-9,4 are the roots

turbid valve
#

If 81 / 3 = 27 (and no remainder), then 3 is a factor of 81

#

Same logic

midnight pier
#

ahhhhhh

turbid valve
midnight pier
#

-5

turbid valve
#

the term factor was x +5

#

So the root is -5 yh

midnight pier
#

Yhhhhh

#

So is that all there is to it?

turbid valve
#

ye

#

there was something else you've mentioned, ...

turbid valve
midnight pier
#

huh

#

YE

turbid valve
#

What formula do you have?

midnight pier
#

i heard the top sets doing it and

#

If i do it next year

#

Then

midnight pier
#

Im talking bout the big one

turbid valve
#

fyi there are a few

midnight pier
#

O

#

Uh

turbid valve
#

(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?

midnight pier
#

Lmao bro saw his work “ by accident”

midnight pier
turbid valve
midnight pier
#

Lmao

#

Soo

#

Rearrange

turbid valve
#

Now, the actual method to do that is not really that obvious

#

Let's see if I can't find a good explanation somewhere...

midnight pier
#

I mean your making it t^3 +pt +q.

midnight pier
turbid valve
midnight pier
#

multiply by x…

turbid valve
#

(this is where I look through my uni notes to see if I might find something girlbleak )

turbid valve
#

This being the search term

midnight pier
#

DAMN

#

This is

#

Hard

midnight pier
turbid valve
#

yh, dw too much about it, it's rather a lot for someone not used to seeing tons of algebra lol

turbid valve
midnight pier
midnight pier
#

Loads of modules then..

turbid valve
#

Like what AQA and Edexcel do with their exams tho

#

It's semi-random

#

There's no "this is 0001, this is 0002, etc"

midnight pier
#

Ohhhhh

turbid valve
#

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

midnight pier
#

Where has w come fromv

#

?

turbid valve
midnight pier
turbid valve
#

for s?

midnight pier
#

Yhh

turbid valve
#

There's just one equation tho?

turbid valve
midnight pier
#

Ah fuck im tapped

#

I meant x

turbid valve
#

ah lol

#

There're three roots at most for x in a cubic

midnight pier
turbid valve
#

So we can get them with 3 equations

midnight pier
#

Ahhhh

#

How do you get those 3?

turbid valve
#

(not unlike taking the plus or minus from the quadratic)

turbid valve
turbid valve
#

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

midnight pier
#

How do they get the equation for the roots? Do they js make it up or sum

turbid valve
#

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

midnight pier
#

Ohhhhh

#

Thats a handy trick tbf

turbid valve
#

I've stolen the cubic's antidepressants turned this into a depressed cubic

midnight pier
#

Hahaha

#

Js withheld the depressants

turbid valve
#

Now it turns out we've known solutions to these for centuries

midnight pier
#

O

turbid valve
#

[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]

turbid valve
midnight pier
#

So its js rearranging in a nutshell

turbid valve
#

ye

midnight pier
#

Ahhhh i see

turbid valve
#

The rest of that PDF involves making some more snarky substitutions to get some nifty formulas

midnight pier
#

Maths on energy drinks surely breaks laws somewhere

turbid valve
#

The reason these are uni-level explanations at all btw is to do with the context they're in

midnight pier
turbid valve
#

Namely - there is a quadratic formula (you learn this in school)

midnight pier
#

yh

#

Isnt there some quartix one

turbid valve
#

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

midnight pier
#

Ahhhh

#

I see

turbid valve
#

after this sorry excuse for a line lol

midnight pier
#

Ik the set one

#

I think

turbid valve
#

yh they explain these along the way, but it's pretty weird to immediately apply this

midnight pier
#

truuu

turbid valve
#

ProofWiki's is easier to use as a tool

#

Now, the question is - does this generalise?

midnight pier
#

Like generalize

turbid valve
#

Is there a formula for any polynomial?

midnight pier
#

Uh

turbid valve
midnight pier
#

O thats a question

#

A good one

#

If there was

#

That would be useful

#

So like if highest power = z: use this and etc

turbid valve
#

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"

midnight pier
#

Lmao

#

Is quintic x^5?

turbid valve
#

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

midnight pier
turbid valve
#

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)

midnight pier
#

So a group is a lot of rings?

turbid valve
#

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"

midnight pier
#

Yhh

#

Kk

turbid valve
#

[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]

midnight pier
#

Lmaoo

turbid valve
#

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?"

midnight pier
#

K

turbid valve
#

(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"

midnight pier
#

Kk

turbid valve
#

That last statement - we've proved some-the- girlbleak -how - is false

#

So actually there's no quintic formula

midnight pier
#

O

#

turbid valve
#

(thus by extension there's no sextic or septic equations etc. (yes those are actual words wtf is this language even))

midnight pier
#

Is thatcus of the galois group thing

#

🤣🤣🤣🤣

turbid valve
#

ye

#

Some Galois groups are solvable

midnight pier
turbid valve
#

That of the quadratics is, for instance, which is why there's a quadratic formula

midnight pier
#

kk

turbid valve
midnight pier
#

so its quartic then quintic

turbid valve
#

ye

#

cf. "quarter"

midnight pier
#

Ahhhh

turbid valve
#

Anyways there you go, a shitty crash course on a third-year UG maths module opencry

midnight pier
#

Lmao much appreciated

#

W crash course

#

Awesome and tnaks for the help with the cubics aswll

#

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#
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#
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lavish mortar
#

Hi, I just have a question about a step taken in a worked solution for an initial value problem

lavish mortar
scenic condor
lavish mortar
#

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

normal hollow
#

s²+pi²/4 -s² in numerator

lavish mortar
lavish mortar
normal hollow
lavish mortar
#

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

normal hollow
#

And i m not sure how they got thaat either

lavish mortar
#

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 😅

normal hollow
#

It's not js that term tho,is it

#

It's the whole function

#

, no?

woeful trench
#

(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?)

woeful trench
woeful trench
lavish mortar
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I will send them now 1 sec

lavish mortar
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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

woeful trench
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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)

lavish mortar
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just done, will send my values for the decomp here

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I am mainly hung up on why he did not decompose directly like this

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sry if this is very basic stuff, I am pretty lost in this topic

woeful trench
# normal hollow s²+pi²/4 -s² in numerator

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 FubukiThis)

woeful trench
lavish mortar
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what does that mean 😭

woeful trench
lavish mortar
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did I break a rule?

lavish mortar
woeful trench
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Yea, try out the work again, but take the decomposition to be $\frac{A}s + \frac{Bs + C}{s^2 + \frac{\pi^2}4}$

rocky lotusBOT
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@woeful trench

woeful trench
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And lemme see if I can find something for you catlove

lavish mortar
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ah so this is the form you need

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I would really appreciate it thanks

woeful trench
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e.g. like this one here (which is more clearly explained by their example than by the screenshot Bruh)

lavish mortar
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omg

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thank you man

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😭

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so what I did was rubbish

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this makes sense

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Imma do it again

woeful trench
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Yep you should see it works out if you do it that way SCgoodjob2

vale dockBOT
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@lavish mortar Has your question been resolved?

lavish mortar
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I did it but didnt factor exp(-5s) back in

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A and B aren't nonsense now at least

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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

vale dockBOT
#
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lavish mortar
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got it, I made a stupid

vale dockBOT
lavish mortar
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thanks baring with me

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.close

vale dockBOT
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vale dockBOT
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Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
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orchid thistle
#

Hello, Rational Inequalities.
(2x/(x-4))≥1

orchid thistle
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Hello i have returned from a quiz @toxic ridge

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i checked out the wavy curve thing and I still dont understand it

ivory valley
orchid thistle
ivory valley
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What's a number graph?

orchid thistle
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the Straight Line

ivory valley
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Oh

orchid thistle
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lik ds

ivory valley
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So you are basically asking for the solution?

orchid thistle
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he called it the number graph so idk

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somewhat

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the intervals

ivory valley
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Okay

orchid thistle
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how to know the intervals ig

ivory valley
orchid thistle
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(x+4)/(x-4)≥0 i got ts

ivory valley
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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.

rocky lotusBOT
orchid thistle
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yez i got (x+4)/(x-4)≥0

ivory valley
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Ok nice