#help-49

1 messages · Page 62 of 1

west iron
#

you just have to show that multiplying a number by d (single digit) will never be bigger than adding a d in front of it

fleet moss
#

i think this could work yeah. your base cases are just trivial 0-9

twilit field
grand pondBOT
#

ƒ(Why am. I here)=I don't Know

west iron
#

gamma is number of digits?

#

then you are incorrect

twilit field
#

yes

west iron
#

for example, adding a 9 in front of 37 increases the number by 900

#

which is less than 10^(2+1)

twilit field
#

ah, right

#

by $\leq 10^{\gamma +1}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

fleet moss
#

why not think about multiplication than addition

west iron
#

additive difference can be used to get at the geometric difference

#

i would think about both operations (multiplying by d, and adding a d at the front) in terms of the additive increase they give

fleet moss
#

i mean we can also consider adding a digit to the end rather than the front

#

makes it considerably easier imo

burnt flame
#

wait...

#

hmm

twilit field
fleet moss
#

i think

west iron
#

oh fair enough

fleet moss
#

i have a solution in mind but im too sleepy to know whether its right

west iron
#

that works as well

twilit field
#

hmm

#

so adding another digit , moves the number by $\geq 10^{\gamma}$

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say I have 100

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I 1add another zero

#

ok, yeah, makes sense

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

so $0 \leq g(n) \leq 10^{\gamma}$

burnt flame
#

leq

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

$g(n)= n_1 n_2 n_3....n_{\gamma}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

how all these numbers are less than or equal to 9

#

so in the largest case I have $0 \leq 9^{\gamma} \leq 10^{\gamma}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

which is true $\forall \gamma \geq 1$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

any any other sequence of gamma numbers is less than $9^{\gamma}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

thus we have our proof

#

is that it?

#

I feel I have to prove that the maxium product is $9^{\gamma}$ though

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

fleet moss
fleet moss
twilit field
#

$g(n) = n_1 n_2 ....n_{\gamma}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

this is maximised when $n_1=n_2....=9$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

fleet moss
#

that part makes sense eah

#

but what about n?

twilit field
#

n?

twilit field
twilit field
#

I don't know how to explain it, it just makes intutive sense to me

#

like say there are $\gamma-1$ 9s

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

and some other arbitary digits

fleet moss
twilit field
#

then we have the product is $9^{\gamma-1} \alpha$ where $\alpha$ is the random number

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

fleet moss
#

i think in general you dont have to think about the total number of digits at all if youre doing it inductively. but youll need to think about multiplication rather than addition

west iron
#

man you really gotta find easier problems to solve

twilit field
#

I'm practising hard problems to get acquainted with proof writing before I start uni

west iron
#

are there easier proof problems you can find

twilit field
#

I guess? I'm just using this as a benchmark as it's from the hardest maths exam school going kids in my country write

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save for olympiads

west iron
#

it's probably ideal to work on problems that you at least stand a chance of solving by yourself

twilit field
#

true

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thanks

west iron
#

np

twilit field
#

.close

midnight plankBOT
#
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fleet moss
#

oh i mean i think you can do this one though, at least the first part

midnight plankBOT
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twilit field
#

3 is a common divisor of 6, 9, and 15., write a logical statement representing this

twilit field
#

Let the statement 3 is a divisor of 6 be P,9 be Q and 15 b %

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then $P\wedge Q\wedge R$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

deep vine
#

so like what's your question

twilit field
#

is this right?

deep vine
#

yea

twilit field
#

that's all, thanks

#

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viral dagger
#

$$a+x^2=2006$$
$$b+x^2=2007$$
$$c+x^2=2008$$
$$abc=3$$
find $\frac{a}{bc}+\frac{b}{ac}+\frac{c}{ab}-\frac{1}{a}-\frac{1}{b}-\frac{1}{c}$

grand pondBOT
#

Skill_Issue

midnight plankBOT
#

@viral dagger Has your question been resolved?

midnight plankBOT
#

@viral dagger Has your question been resolved?

last slate
#

@viral dagger

viral dagger
#

huh

last slate
viral dagger
#

$\frac{a^2+b^2+c^2-ab-ac-bc}{abc}$

grand pondBOT
#

Skill_Issue

last slate
#

yes

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now

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lets just consider the numerator

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$a^2+b^2+c^2-ab-ac-bc$

grand pondBOT
#

Cnidarian

last slate
#

multiply it by 2

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$2(a^2+b^2+c^2-ab-ac-bc)$

grand pondBOT
#

Cnidarian

last slate
#

You can write this as sum of sqaures of 3 terms

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do you see how ?

viral dagger
#

$(a-b)^2+(a-c)^2+(b-c)^2$

grand pondBOT
#

Skill_Issue

viral dagger
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ooh

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ok ic, ty

#

let $x-y=1$, find $$x^4-xy^3-x^3y-3x^2y+3xy^2+y^4$$

grand pondBOT
#

Skill_Issue

last slate
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Is this related to the same question ?

viral dagger
#

no

last slate
#

Okay

viral dagger
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nvm lmao i solved it, sorry

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uh lemme find a diffrent question

last slate
viral dagger
#

$$x+\sqrt{xy}+y=9$$
$$x^2+xy+y^2=27$$
find $x-\sqrt{xy}+y$

grand pondBOT
#

Skill_Issue

viral dagger
last slate
#

and the subtitute the second equation into it

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Get it ?

viral dagger
#

uh ill try

last slate
#

This question is similar to

#

Say

viral dagger
#

$xy+x\sqrt{xy}+y\sqrt{xy}=27$

grand pondBOT
#

Cnidarian
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

viral dagger
#

oh

grand pondBOT
#

Skill_Issue

last slate
#

yeah

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gtg

viral dagger
#

i tried squaring the second equation, i got $$2xy-2x\sqrt{xy}-2y\sqrt{xy}+27$$

last slate
viral dagger
grand pondBOT
#

Skill_Issue

last slate
#

you odn't have to do that!

viral dagger
#

huh

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OH

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ok nvm

viral dagger
grand pondBOT
#

Skill_Issue

last slate
#

no...

viral dagger
#

whar

last slate
#

gtg bye

viral dagger
#

bye

#

it was 3 :p

#

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viral dagger
#

if $x=\sqrt{19+8\sqrt{3}}$, find $$\frac{x^4-6x^3-2x^2+18x+23}{x^2-8x+15}$$

grand pondBOT
#

Skill_Issue

upper crag
#

just curious what course is this

low finch
#

i wonder wtf is this

twilit field
#

olympiad maths maybe

sly ravine
#

Patience Algebra

low finch
#

wow

wary trail
#

are you wanting a hint or just how to do it

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since yeah it looks like competition maths

low finch
#

method 1: change x into the roots and calculate it (very real and siemple)

old storm
#

goddamn, cant even use rational root theorem to simplify that one above, you have to actually play with it

twilit field
#

chcek if $x^2-8x+15$ is a factor of the numerator first

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

old storm
#

(x-3)(x-5) btw

twilit field
#

,w (x^4-6x^3-2x^2+18x+23)/(x^2-8x+15)

low finch
#

wat

sly ravine
#

Stap

twilit field
#

ok, that won't help

low finch
#

whats the answer

upper crag
#

if you call the numerator f(x) then f(x-1) is eisenstein for p=2 (so it's irreducible)

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(although knowing 3, 5 are roots of the denominator and are not factors of +-1, +-23 already means there is no cancellation)

midnight plankBOT
#

@viral dagger Has your question been resolved?

viral dagger
hard umbra
#

just find the min poly of x and divide bending_skull

#

why so complicated

viral dagger
hard umbra
#

,w min poly of sqrt(19 + 8sqrt(3))

hard umbra
#

that tells you already that the denom is 2

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and now you just do like

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,tex<polynom> \polylongdiv{x^4 - 6x^3 - 2x^2 + 18x + 23}{x^2 - 8x + 13}

grand pondBOT
low finch
#

w

hard umbra
#

which means the numerator is 10

viral dagger
#

huh

#

how can you just get 10

upper crag
hard umbra
#

because
[ x^4 - 6x^3 - 2x^2 + 18x + 23 = (x^2 + 2x + 1)(x^2 - 8x + 13) + 10 ]

grand pondBOT
hard umbra
#

just work it out by hand

viral dagger
#

what do you do after that

hard umbra
#

x^2 - 8x + 13 = 0

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,, \sqrt {19 + 8\sqrt 3} = \sqrt {4^2 + 2 \cdot 4 \cdot \sqrt 3 + 3} = 4 + \sqrt 3

grand pondBOT
hard umbra
#

(x - 4)^2 = 3

viral dagger
#

what do you do with the 10/x^2-8x+15

hard umbra
#

x^2 - 8x + 15 = x^2 - 8x + 13 + 2 = 2

viral dagger
#

wait

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oh sorry

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lemme work it out

grand pondBOT
#

Skill_Issue

viral dagger
#

wait no

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wait yea

#

is this correct?

hard umbra
#

what did you do there

viral dagger
#

oh sorry i misread something

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its 5?

hard umbra
#

yes

viral dagger
#

oh

#

thanks

#

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twilit field
#

Which of the following expressions are well-formed formulas?:-

$\left(P\wedge Q\right)\left(P\vee R\right)$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

how do I even interpret this

#

I feel it isn't a well formed formula

dreamy lichen
twilit field
#

thanks!

#

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last slate
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viral dagger
midnight plankBOT
viral dagger
#

.close

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last slate
#

Okay

midnight plankBOT
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twilit field
#

How do natural numbers have a decimal expansion

zealous schooner
#

it just means the digits

twilit field
#

ah

zealous schooner
#

decimal expansion because we use a decimal system

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like a base 10 system

twilit field
#

so I now effectively find the number of solutions to $x+y+z=10$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

and then permute them

zealous schooner
#

yeah

#

x,y,z>=0

twilit field
#

yeah

#

thanks

zealous schooner
#

except x cant be 0

sage helm
#

sure it's not meant to be 3.000000000...

twilit field
sage helm
#

never heard decimal expansion being used for any other context

strong lava
#

that's very quickly enumerated

twilit field
#

wait, why should y or z be 0

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oh

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ok

strong lava
#

(ii)

twilit field
#

so if 0 appears twice there are 9 such numbers

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zero appears once in 144 numbers

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so the answer 153

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wait

#

no

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the solutions are $(1,9);(2,8);(3,7);(4,6);(5,5)$

#

this into 2

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

wait

#

shit

#

let 0 appear twice

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there are 9 such numebrs

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let 0 appear once

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so I have $[(1,9),(2,8)(2,7),(4,6)(5,5)]$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

as possible solutions

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which gives me an answer of 18

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ok, but how would i count without listing it case-wise

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<@&286206848099549185>

simple field
twilit field
#

by listing the solutions out

twilit field
#

now (z,y) is also valid

simple field
#

a three digit number ABC has the following properties:
one of A, B, C is 0, A cannot be 0 because it would then be at most a 2 digit number. so B or C is 0
let x = A, y = max(B, C) i.e. it is the non-zero number
x + y = 10 and 1 <= x <= 9, so there are 9 solutions (x, y)
for each solution (x,y) we can have either B = y, C = 0 or B = 0, C = y
so the total number of solutions is 2 * 9 = 18

#

which seems to be basically what you did, nothing wrong with listing out solutions to verify your calculations

#

especially when there arent a ton of solutions listing is worth doing, a sanity check

twilit field
#

Yeah, I get that

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but what if there say 100+ solutiosn

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*solutions

simple field
#

yeah then not so much haha

twilit field
#

thanks!

#

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twilit field
#

here do I assume digits can be repeated?

midnight plankBOT
twilit field
#

nvm

#

we do

#

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last slate
#

Does my expression look correct for a quadratic? Was this just an error of not adding 6 decimal places?melody

midnight plankBOT
#

@last slate Has your question been resolved?

carmine sigil
#

@last slate so the model you have is obviously wrong, because the model should have a maximum, but your a value is positive, indicating a minimum instead at some point

#

How did you arrive at this model?

last slate
last slate
carmine sigil
#

And your calculator gave you a positive value for the a coefficient?

carmine sigil
#

Can you show me?

junior flower
last slate
carmine sigil
#

That's a negative a

last slate
carmine sigil
#

a is the coefficient

#

It's appearing as negative on your calculator, but you entered it as positive in the answer box

#

Simple data entry error

last slate
carmine sigil
last slate
#

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last slate
#

.reopen

midnight plankBOT
#

last slate
#

On part c I'm a little lost. Part d I put 350 since it the value of profit went down.

split jetty
#

aka the peak of profit

last slate
last slate
split jetty
last slate
#

Sorry for budging in

split jetty
last slate
#

noblobcry

split jetty
#

that function tells you the total gain of money, when x=ticket price

#

so to find when the function increases or decreases, you need to find the derivative

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@last slate did you understand it?

last slate
split jetty
#

only if you want to find when they get 0 dollars kekw @last slate

#

@last slate do you know what is a derivative?

split jetty
#

yea

last slate
#

would it invlove the slope theb

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then

split jetty
#

for example: if I the ticket is 1 dollar more expensive, will I get more value than just not changing the price

last slate
#

yes...

split jetty
last slate
#

ok

split jetty
#

lets say you sell tickets for 0 dollars, then you will get 0 dollars in total

last slate
#

its making more sense now

split jetty
#

but if you sell tickets for 1000 dollars, you will gain something, but very few people will buy it

last slate
#

That makes sense

split jetty
#

well there is a point in the middle where you gain even more than those 2 cases

#

and well that point, even if you add or subs 1 dollar, you will lose on some benefit

#

is it good now? @last slate

last slate
split jetty
#

imagine this is the benefit (very simplified version)

#

you want to find that peak

last slate
#

Okay gotcha

split jetty
#

the function is: -x^2 + x + 5

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so to find the peak, we have to take the derivative

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and at the peak the derivative is always 0

last slate
#

Okay so could be a derivative elsewhere with a different value

split jetty
#

the black line is the derivative of that function

last slate
#

aside from the peak i mean

last slate
split jetty
#

idk is there anything else? @last slate

last slate
#

No, TYSMMM🫶

#

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gritty hatch
#

uhm...

midnight plankBOT
gritty hatch
#

Ok, so, if I'm guessing correctly.

#

Is this impossible?

sweet wing
#

impossible how?

gritty hatch
#

I don't see how you could factor that.

onyx cedar
#

you can

gritty hatch
#

I can't even solve one of them after spending innumerable hours thinking about how.

#

Without a method.

#

Just trying to factor it raw.

twilit field
#

Quadratic formula

gritty hatch
#

And then I don't even know how this relates to graphs or what roots are.

gritty hatch
#

not allowed

#

just raw

sweet wing
#

wdym just raw

gritty hatch
#

is there a realistic way you could look at that and just factor it through mental calculation

shrewd wagon
#

(3x-1)(x+2)

gritty hatch
#

bc thats literally what they did

sweet wing
#

why wouldnt you be allowed to use the quadratic formula

gritty hatch
#

cuz they didnt give me it in the video

#

and they expect you to just solve it

onyx cedar
#

i jus split up the linear term, seperate them into two brackets, factor out the gce of each bracket and then cross one of them out

gritty hatch
#

see what im really asking is for the narrowing logic they used

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this is what everyone seems to not get about what im asking

#

the only way i could see this being solved is narrowing

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like seeing what combinations would end up giving you 5x and 2 while considering the pieces given

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without actually calculating anything

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sort of like estimation

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cuz clearly this isnt possible outright unless you're superhuman

shrewd wagon
#

(3x-1)(x+2) is factored form

onyx cedar
#

so you wanna know how to factor simple and complex trinomials without having to write down calculations?

#

and just do it as fast as possible?

gritty hatch
summer ravine
#

a+b = 5
ab = -6

gritty hatch
#

in the video he seemed like he just magically got all the answers by writing out factors

summer ravine
#

which grade are you in?

#

@gritty hatch

gritty hatch
#

post school

shrewd wagon
#

you can see that the first term is 3

summer ravine
#

Ok

gritty hatch
#

mmm... oh thats a bother.

#

Im still not being perfect as I should

shrewd wagon
#

so you can write (3x- )(x- )

gritty hatch
#

that will take an adjustment

shrewd wagon
summer ravine
#

list factors of ca and find a pair that satisfies b = sum of factors.

shrewd wagon
summer ravine
#

c*a

gritty hatch
#

hm...

summer ravine
#

it works for a = n also.. i'll go now.
For integers it's quite easy. For fractions you can assume them to be of some sort of form.

#

ok

midnight plankBOT
#

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novel cobalt
#

if x is in set of real numbers, then the limit doesnt exist right?

hearty rune
#

yeah

novel cobalt
#

.close

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bleak pier
midnight plankBOT
bleak pier
#

sin^2(90-18)-3/4

#

cos^2(18)-3/4

#

<@&286206848099549185>

summer ravine
#

Yes dear?

#

,w sin^2(72)-sin^2(60)

last slate
#

Whole eqn becomes

#

God damn

#

Ok basically

#

Convert sin 72 into cos 18

#

Then using double angle formula

#

The whole equation simplifies to

bleak pier
#

@dusky flint

last slate
#

(2Cos 36 -1)/4

dusky flint
#

I see

last slate
#

Ah im on my phone

#

Ypu guys continue

bleak pier
last slate
#

Convert the cos into sin

#

Then you know the value of sin 60

bleak pier
last slate
#

Use double angle formula

dusky flint
#

well its pretty simple

dusky flint
#

true

dusky flint
last slate
#

sorry guys I'm on my phone so i can't do calculations 😭

#

I can but it's like 1 am

dusky flint
#

it becomes cos^2(60)-cos^2(72)

dusky flint
#

but its ok i can do it

dusky flint
#

then u use double angle formula to find cos(72)

#

therefore cos(72) = 2cos^2(36)-1

#

now cos(36) = phi/2 = (1+root(5))/4

bleak pier
#

sin^2(72) becomes -cos^2(72)?

dusky flint
#

1-cos^2(72)

bleak pier
#

i see

#

got it

dusky flint
#

yup

#

then ur cos(76) becomes [root(5)-1]/4

#

now substitute the value

#

and you have your answer

#

anything else?

bleak pier
dusky flint
bleak pier
#

i only know 30 45 60 90

#

could you tell me what are others which are helpful?

#

18 36 15 75?

last slate
#

15,75 ofc

#

Use sin(60-45) for that derivation

bleak pier
#

ohh got it

last slate
#

Or sin(45+30)

bleak pier
#

sin60 cos 45-cos60 sin45

dusky flint
last slate
#

I smell aspirant

dusky flint
#

it has some which r imp n useful

bleak pier
#

ye

dusky flint
#

wait a min imma tell u

bleak pier
#

nice

dull yoke
#

My dark side beast mode is very dangerous...

bleak pier
dull yoke
last slate
#

Like

#

Sin(3×18+2×18) =sin 90

#

Then sin addition formula

#

Then triple and double angle formula

dusky flint
#

well they have good identities and all

#

it has a good base

bleak pier
#

Tq so much bhai

dusky flint
#

and additionally i would recommend learning how to find those unique angles through patterns

#

instead of remembering it will give you a better order of thought

#

for example your 72 degrees could be rewritten as 2(36) = 2(2(18)) = 2(2(90/5))

#

you could have found it using those formulas above

last slate
#

Just remember sin 18 and cos 36 haha. Others can easily be came up with, with sin,cos(90-36,18)

dusky flint
#

no need to remember them

last slate
#

Yea but that takes time

dusky flint
#

hmm true well i m good at quick calculations then haha

last slate
#

If I'm in an exam and start deriving sin 18, im 101 percent dead lmao

dusky flint
#

haha then where do i belong lol

#

i have bad memory power so i derive formulas in exams

#

and also create methods to solve problems without those formulas during the exams

last slate
#

damn

dusky flint
#

yeah i have a 1000x brain power in solving logical questions but 0 for memory

last slate
#

that's coool

dusky flint
#

🥲

#

not cool at all

#

i can do maths and phy

last slate
#

Yea but

dusky flint
#

but as a jee student i need chem as well

#

but i cant remember even a bit of it

last slate
#

you're in 12th?

dusky flint
dusky flint
last slate
#

im in 11th :]

dusky flint
#

oh nice

#

u prepping for anything?

last slate
#

jee

#

Lmfao

dusky flint
#

oh make sure to have good grasp on basics of every concept

#

especially organic chemistry or u gonna cry like me later

last slate
#

we haven't even started organic yet :]

dusky flint
#

oh damn

last slate
#

just mole concept thru chemical bonding for now

dusky flint
#

yeah its the first month i see

#

where u frm?

last slate
#

uhh country or state or what?

dusky flint
#

state/city ig

#

country ofc ind

last slate
#

punjab

#

near punjab

dusky flint
#

ohh

last slate
#

Around

#

Yk

dusky flint
#

i m from gujarat

last slate
#

nicee

dusky flint
#

yup

#

well u should ask your teacher to teach you interconversion formulas for concentration terms for mole concepts

#

they r really useful

#

for solutions ch in 12th

last slate
#

yea they taught us that

sage olive
#

yoo fellow gujarati spotted

last slate
#

Still haven't remembered

dusky flint
last slate
#

I just converted on spot

dusky flint
#

kya thi?

dusky flint
sage olive
#

technically america lol

#

but my family’s gujarati

dusky flint
#

aree haha

#

hu surat thi

#

i am oswal jain

last slate
#

bhai ye kya collab hai 😭😭

dusky flint
last slate
#

so anyone suffering from chronic depression

#

I know I will be

dusky flint
#

everyone after taking jee

#

i m srsly worried abt my jee percentile after knowing i get 0s on organic

#

and 90s and 100s on maths

#

and around 60-70 in phy

last slate
#

I am loving physics rn man

#

nlm and wpe

dusky flint
last slate
#

Oof

#

Sexy

dusky flint
#

i also felt the same at first

#

but its crying later

#

rotational motion

#

and many more things make u cry

#

even in 11th

last slate
#

I've heard myths about rotational motion

#

Can't believe round stuff caused so many problems

dusky flint
last slate
#

🚲🚲💿💿🚵‍♂️🚵‍♂️ boo

dusky flint
#

initially everything was calculated as straight lines or figures

#

but when wheel was made

#

it made everyting complicated

last slate
#

The problem started in 3000 bc

dusky flint
#

because now after you can do smtg called rectiilinear movement

#

so mathematicians developed trignometry

last slate
#

Nd vectors

#

love vectors

dusky flint
dusky flint
#

basics are easy

#

applying it to harder concepts is tougher

last slate
#

Like the WET or something?

dusky flint
#

WET?

last slate
#

Work energy theorem

#

Just did it yesterday

dusky flint
#

nah its pretty simple

last slate
#

Right 🙂

dusky flint
#

there are derivations more complex

last slate
#

I'm cooked

#

Medium rare

dusky flint
#

but lets just say if u have a good base n good analytical brain u can somehow survive

#

and u also need good memory power

#

good enough to remember around 1000 reactions of organic chem

last slate
#

interesting

#

Hmmmmmmmmmmmmmmmmmmm

#

im gonna

#

ok

#

possible

#

Can I friend you?

dusky flint
#

okk try then

dusky flint
last slate
#

hey i love tech n swimming as well

dusky flint
#

oh niceeee

#

i love them

midnight plankBOT
#

@bleak pier Has your question been resolved?

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terse mesa
midnight plankBOT
terse mesa
#

need help on b

#

i think im braindead

small jasper
#

It's just asking for (number of factors of 24 that are odd)/(number of odd numbers)

terse mesa
#

wouldnt that be 7/6

#

anyone

small jasper
terse mesa
#

sorry, i looked at all numbers in F and intersection

#

over all numbers in 0 and intersection

#

but idk what other answer it can be, ik 7/6 wont even work cause pb isnt like that

#

but what is the answr

#

and how?

small jasper
#

edited my original for clarity

#

tho you should also note that 13, 14, and 15 aren't in the venn diagram

terse mesa
#

oh yeah

#

so 2/8?

#

1,3/1,3,5,7,9,11,13,15

small jasper
#

simplify it but yeah

terse mesa
#

yh 1/4

#

luv bro

#

god bless

small jasper
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terse mesa
#

.close

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steady vigil
#

Hello, I need help with solving this Augmented Matrices. It’s my first time and I’m confused on what of the 3 Elementary Row Operations to use.

steady vigil
#

I already started partially with help from someone but I had to leave.

fallen vigil
#

What operation did you do

steady vigil
#

I did this: Add a Multiple of One Row to Another Row: Replace one row with the sum of that row and a multiple of another row.

#

I subtracted 2 from the 2nd row getting 0 in the bottom left hand column.

fallen vigil
#

Im assuming you tried to do 2nd row - twice the first row ? If so your calculation is off

steady vigil
#

What?

#

I subtracted 2 from the first row.

fallen vigil
#

Ok yeah you can’t just subtract constants

steady vigil
#

Ok,

fallen vigil
steady vigil
#

I’m confused about the rule though.

fallen vigil
#

You are correct that you want to get the bottom left element as 0 but you have to subtract a constant multiple of an entire row to do this

steady vigil
#

Ok, don’t you have to do one of the three Elementary Row Operations to get 0?

fallen vigil
#

Yeah

steady vigil
#

Which are: Interchange Rows: Swap the position of two rows in the matrix.
Multiply a Row by a Non-Zero Constant: Multiply all elements of a row by the same non-zero value.
Add a Multiple of One Row to Another Row: Replace one row with the sum of that row and a multiple of another row.

#

The only one that works is the last one.

fallen vigil
#

Yup. So you want add a constant multiple of a row to the 2nd row, since there are only 2 rows you will have to add a constant multiple of the 1st row to the 2nd row

steady vigil
#

Oh so you add that element and a coefficient from another number. Is that correct?

fallen vigil
#

Yeah and that coefficient should be constant across all elements of the row

steady vigil
#

Aren’t none of the coefficients constant since the x and y coefficients vary on each row?

#

Could I continue this later? I have to go.

fallen vigil
#

Yeah

midnight plankBOT
#

@steady vigil Has your question been resolved?

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low finch
#

ok i hate this

midnight plankBOT
neat hamlet
#

look the the numerator compared to the denominator of each term

midnight plankBOT
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@low finch Has your question been resolved?

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twilit field
#

Simplify the following statements. Which variables are free and which are bound? If the statement has no free variables, say whether it is true or false.

$\left{5\notin\ \left{x\in\mathbb{R}\right|13-2x>c\right}$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

so firstly, I feel that both x and c are free variables

#

now I know this is wrong

#

the thing though is , intuitively, both x and c can vary, right?

midnight plankBOT
#

@twilit field Has your question been resolved?

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lusty cave
#

Can someone help me to solve this I dont know where to start

shell berry
#

think of the graph of the absolute value of x

lusty cave
#

hmm

shell berry
#

,tex
$
\begin{cases}
|x|=-x, x<0\
|x|=x, x>0
\end{cases}
$

grand pondBOT
lusty cave
#

what intervals do I find

shell berry
#

does this look familiar

lusty cave
#

oh

#

ig

shell berry
lusty cave
#

i see

#

]ok

shell berry
#

to flip it upside-down, turn it into -|x|

lusty cave
#

so how do i determine what Y equals

shell berry
#

so y= some transformation of |x|

lusty cave
#

😭

shell berry
#

not an exact value

#

do know how to transform functions?

lusty cave
#

no

shell berry
#

alright give me just a moment

#

Use the sliders to look at how each variable effects the function

#

fixed

#

s changes the vertical scale
a changes the horizontal offset
b changes the vertical offset

shell berry
#

,tex $y=-|x-1|-1$

grand pondBOT
shell berry
midnight plankBOT
#
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twilit field
midnight plankBOT
twilit field
#

nvm

#

.close

midnight plankBOT
#
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twilit field
#

.reopen

midnight plankBOT
#

twilit field
#

why Can't I solve this by equating the two functions?

#

so $x^3+ax+1=x^4+ax^2+1$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

if they share a common root, the above will hold true

#

so that gives $x=-a$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

just drop a hint please

#

what am I missing

last slate
#

i think its wrong, cus having a common root doesnt mean the functions can be equal

twilit field
#

oo

#

$x^2=-a$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

which is only possible at a=0

twilit field
#

at that point

twilit field
hard shard
#

so whats your answer

twilit field
#

a=0

#

so only one value

hard shard
#

are you sure?

twilit field
#

oh

#

a can be negative]

#

right

#

but $\infty$ isn't the answer, is it

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

hard shard
#

make sure theyre solutions to the original equation

#

s

last slate
#

mb

twilit field
#

I'm getting x^4+ax^2+1. evaluvated at x^2=-a is 1

hard shard
#

so that means?

twilit field
#

there' no such $a \in \R$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

hard shard
#

but alas there is

twilit field
#

0

hard shard
#

think about where you may have discounted a solution

twilit field
#

hmm

#

x=1 is a valid solution

#

for f(x)=g(x)

hard shard
#

so is x=0, but its clear that you end up with 1=0 again

twilit field
#

hmm, so one thing I know is $a$ has to be negative

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

did I discount a solution by canceling out the 1s?

#

nah, that's silly

fleet moss
#

what about cancelling out x

cobalt sigil
#

Real roots or any roots ?

twilit field
#

real roots

twilit field
#

$x^3(1-x)+ax(1-x)=0$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

$(x^3+ax)(1-x)=0$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

cobalt sigil
#

So a = -2

fleet moss
#

mhm and then

twilit field
#

x=1

cobalt sigil
#

Thatz one possible solution

fleet moss
cobalt sigil
twilit field
#

$x(x^2+a)(1-x)=0$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

if a is negative

#

then$x^2=-a$ will have infinitely many solns

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
#

BUT subbing $x^2=-a$ back into the OG equation doesn't give us 0

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

cobalt sigil
#

So we get only one value x=1 and a = -2

twilit field
#

how did you get$a=-2$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

cobalt sigil
hard shard
cobalt sigil
#

x³+ax+1=0 or 1+a+1=0 or a = -2

twilit field
#

ah

#

catscream That should have been obvious to me

#

thanks

hard shard
#

should be more obvious now

twilit field
#

it is

hard shard
#

youll be quicker the next time you see it

cobalt sigil
#

,w plot y = -(1+x³)/x and y = -(1+x⁴)/x²

twilit field
#

yeah, but if I can't think of such simple solutions, i'mma fail uni once I start it

hard shard
#

do not sweat it

cobalt sigil
hard shard
#

some of my engineering classmates did not know what a dot product was

cobalt sigil
hard shard
#

pure ftw, but also do whatever makes you happy

hard shard
twilit field
#

thanks !

#

.close

midnight plankBOT
#
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twin ridge
#

Anyone able to point me in a direction for this homework? I missed this day of class since I was out of town.

twin ridge
#

From what I can see, the functioning definition I need here is if a sequence is bounded and monotone, then it is convergent.

#

And then to find the limit, I need to figure out if it's increasing or decreasing, then the limit is the sup or inf

#

Admittedly I do not have very much experience with recursive formulas, but I would hazard a guess that the lower bound of this function is 2 and the upper bound is 8

#

I know a lower bound is 2, I don't know if it's the greatest lower bound though.

rose trout
#

Well knowing the bounds is enough for monotone convergence.
Can you show it's increasing or decreasing?

twin ridge
#

I know it has bounds. It looks like it's decreasing by plugging in a few indices. How do I know if 2 is an infimum though?

#

Normally I'd just plug in a really large number to see where it's trending but I can't quite do that with a recursive formula.

wary thorn
#

i'd just compute its limit

#

and then given that its monotone and bounded

#

it converges to its limit

twin ridge
#

How do you compute the limit of a recursive forumla?

#

That's the part I'm stuck on

rose trout
#

Let's say we start by knowing it converges.

wary thorn
#

then take lim of both sides

rose trout
#

Then we take the limit on the LHS

#

And on RHS

#

x_{n+1} tends to L

#

so does x_n

wary thorn
#

🤝

#

I'd use L instead of x personally

rose trout
#

Good idea

twin ridge
#

Do we know it converges?

wary thorn
#

we'll show that later, using monotone sequence theorem

#

but this way, you don't have to show any infimum nonsense

twin ridge
#

The infimum is defined as the limit of the sequence

#

What does "tends to L" mean?

wary thorn
#

yes but its easier to compute the limit than it is to prove something is the infimum

wary thorn
#

suppose x_n -> L as n->infinity

frank wolf
wary thorn
#

then we say x_n tends to L

frank wolf
#

Because not every sequence has a limit

wary thorn
#

What's the point of bringing up this nonsense?

#

this sequence does have a limit

frank wolf
#

Yes, but the way you phrased it is a little confusing

twin ridge
#

A monotone sequence has to have a limit, no?

frank wolf
#

No

wary thorn
frank wolf
#

Or at least, not a finite limit

frank wolf
twin ridge
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Well this one's the first question on the homework so I'm assuming they're not trying to trick me quite yet

frank wolf
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This doesn’t really make sense to me

wary thorn
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I haven't been able to start my explanation yet

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but what I mean is start by assuming it converges

frank wolf
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Right

wary thorn
#

to
"L"

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L = 1/2 (L) + 2

frank wolf
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Mhm

twin ridge
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I understood what you were saying, but that's cuz I'm looking at the book.

frank wolf
#

That I’m fine with

wary thorn
#

then you can justify that it does actually converge

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using MST

twin ridge
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Is the left side "xn"?

wary thorn
#

x_(n+1)=1/2 x_n + 2

#

lim n-> inf x_(n+1) = lim n-> inf 1/2 (x_n) + 2
(assuming the limit exists)

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(and we denote whatever it converges to as L, so...)

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L = 1/2 L + 2

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now solve for L

twin ridge
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Is the limits for the xn terms both L because xn+1 is just a tailed version of xn?

wary thorn
#

yes

twin ridge
#

Ok

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So L=4?

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Wait

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How does that work

wary thorn
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How does what work?

twin ridge
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How is L=4?

wary thorn
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Why do you think that is is not 4?

twin ridge
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I plugged in 3 terms and got down to 5.

wary thorn
#

okay

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did you ever get below 4?

twin ridge
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I haven't gone any farther yet

wary thorn
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haha

twin ridge
#

Decimals are weird.

wary thorn
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well you wont get below 4

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its monotonically decreasing to 4

#

well, it remains for you to show that its monotonically decreasing

twin ridge
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So 8,6,5,4.5,4.25,4.125 etc?

wary thorn
#

perhaps it does something like that

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i haven't computed anything

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I just have faith in the limit you computed already

twin ridge
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So I could say that 4.5 etc is 2*2+r where r<1

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So I could just say the 1/2xn term never goes under 2?

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This isn't quite relevant to the problem, just trying to justify in my head.

wary thorn
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perhaps it'd be easier to show the sequence is bounded below by 0

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I do think you're getting side-tracked

twin ridge
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Well it's definitely bounded below by 2, since x_n can't be negative.

wary thorn
#

very well, then that works

twin ridge
#

So that proves it is bounded.

wary thorn
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so now show its monotone decreasing

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and you're done

twin ridge
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I gotta figure out how to do that

wary thorn
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show that x_(n+1) is less than x_n

twin ridge
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Do I have to use induction?

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Seems like a logical step, I am just not a fan of havign to do it lol

past mantle
#

what kind of math you guys doin?

wary thorn
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Yeah maybe do induction

twin ridge
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Analysis

past mantle
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what kinda of math is it

twin ridge
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It's mostly proofs based.

wary thorn
twin ridge
#

The first half of my class was just proving why algebra works.

wary thorn
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Tag my sir @ rbmuk if you have any more doubts, he will clear them

twin ridge
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Why 1=1, why 5*(-1)=-5, that kind of thing.

past mantle
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oh ok

twin ridge
#

Now I'm in the section of the class where I'm proving calculus

past mantle
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i don't know calculus

twin ridge
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Does anyone really? Lol

past mantle
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i passed geometry

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luckily enough

twin ridge
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I took Geometry last semester 🙂

past mantle
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i took it for my junior year

twin ridge
#

I took it in high school but my college requires it for math majors again.

wary thorn
twin ridge
#

Not a bad idea though honestly.

past mantle
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damn

wary thorn
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Is the base case

twin ridge
#

Gotcha

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x2 being 6

past mantle
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you guys seem cool and i might have to call on you guys for math

twin ridge
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And then I have to show that x(n+1)<xn?

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To be fair, this entire discord is full of cool people.

past mantle
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yea indeed

twin ridge
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I haven't really met anyone that had any ill intentions in here.

past mantle
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im just vibing for the summer before my senior year

twin ridge
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Nice. I wish I was. I was stupid and decided to take 4 summer classes.

past mantle
#

im about to graduate early in december

wary thorn
past mantle
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i need 24 to graduate, i have 20.25 so im not to far off

wary thorn
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use it to show that x_(i+2) < x_(i+1)

past mantle
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always show your work

twin ridge
past mantle
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true

twin ridge
#

Generally a good practice though.

past mantle
#

yea

wary thorn
past mantle
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there to expensive

wary thorn
#

they're

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too

twin ridge
grand pondBOT
#

Narutoes

past mantle
#

im so lost

twin ridge
wary thorn
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I'd just double check all of that work there 😓

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you had the right idea though

twin ridge