#help-10

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nova vale
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obtuse pebbleBOT
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obtuse pebbleBOT
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round pewter
obtuse pebbleBOT
round pewter
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So I understand the 52!/49!

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But I'm so confused on the order matter part

river falcon
round pewter
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Yes

river falcon
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in how many ways u can arrange those 3 cards in a line

round pewter
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Wym line

river falcon
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like put them down

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how many ways

round pewter
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Like 1 2 3

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How does that work

river falcon
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yes

round pewter
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So it has to increase by 1 each time?

river falcon
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no i mean

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in how many ways u can arrange the 3 cards

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or in how many ways u can permute them

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like if u have 2 things a and b then you can either a,b or b,a

round pewter
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Yuh

river falcon
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like that but for 3 things

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so how many times?

round pewter
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Uh 6

river falcon
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right

round pewter
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Cus 3!

river falcon
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now

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if order matters

river falcon
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but its asking for when order doesnt matter

round pewter
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What does it mean order doesn't matter

river falcon
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like

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the order in which u arrange things

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a,b and b,a

round pewter
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Oh but when order matters it has to be what

river falcon
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in the first one i have a at first, in the second one i have at first

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wdym

round pewter
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So like when it doesn't matter it can be like a c b but when it does, does it mean like abc?

river falcon
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so if order matters then a,b and b,a are two different

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but if order doesnt matter then its 1

round pewter
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😭

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So when order matters you count like a jack queen king different as jack king queen?

river falcon
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yes

round pewter
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Okay that makes sense

river falcon
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so here

round pewter
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Because then there are less arrangements

river falcon
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u basically have 6 arrangements of a set of 3 cards

round pewter
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Why is that

river falcon
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because the number of ways u can permute 3 things is 6?

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3!

round pewter
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Alright thanks I gotta go though

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Cya later alligator

river falcon
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okay

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cya

round pewter
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.close

obtuse pebbleBOT
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timid silo
obtuse pebbleBOT
timid silo
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help, tried a lot of attempts

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tried differentiatiing on both sides

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tried e^x(f(x)+f'(x)) form

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not reaching anywhere]

stone vortex
timid silo
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i reached quite far with differentiating on both sides but it looks ugly

timid silo
stone vortex
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oh ok

timid silo
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anyone?

junior granite
timid silo
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ive just been scribbling in my notebook

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applied by parts like twice too

junior granite
junior granite
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why?

timid silo
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because i integrated again

timid silo
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can you sjhow me your working once?

junior granite
junior granite
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but if you differentiate the xg(x)/{e^x+1)
you can compare it with the function that is being integrated

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from there you can find what g(x) will be

junior granite
timid silo
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ill gibve it a shot once again later]

junior granite
timid silo
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i cant understand maths typed 😭

junior granite
unreal musk
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Do you mean you can’t understand it written at all, or that e.g. you’d rather see it with the equation bot?

timid silo
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i cant understand it typed in chat basically

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dont help me yet tho please i wanna give it a shot myself

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i can come back later right if i still dont get it?

junior granite
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${(e^{x}+1)}^{2}$

warm shaleBOT
timid silo
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thank you :)

junior granite
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this thing in the denominator

timid silo
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ye this wilkl get cancelled

junior granite
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yup

obtuse pebbleBOT
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@timid silo Has your question been resolved?

timid silo
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got it

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stupid calculation error

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thanks tho @junior granite

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dreamy shuttle
obtuse pebbleBOT
dreamy shuttle
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someone pls help

obtuse pebbleBOT
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@dreamy shuttle Has your question been resolved?

obtuse pebbleBOT
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@dreamy shuttle Has your question been resolved?

obtuse pebbleBOT
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@dreamy shuttle Has your question been resolved?

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stoic anchor
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how can I find out what digit does the product end with

gilded needle
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is this the product of the numbers 71 through 79? it's kinda hard to read

stoic anchor
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yea

gilded needle
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ok

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do you know about modular arithmetic?

stoic anchor
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nope

obtuse pebbleBOT
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dull heath
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help pls

obtuse pebbleBOT
tardy epoch
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multiply top and bottom by rational conjugate

dull heath
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what's next

tardy epoch
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divide all terms by the largest one

dull heath
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n*6?

manic chasm
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for these type of limits, normally it is easiest to check the rate of change of the terms, so if the bottom term grows faster then it goes to 0, since you are dividing by infinity.

dull heath
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i think thats difficult now. and right answer is not 0

tardy epoch
# dull heath n*6?

largest term being the one that grows the fastest as n goes to infinity

manic chasm
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well, it seems to diverge since the top is so dominate

tardy epoch
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in your case it's n^(3/2)

manic chasm
obtuse pebbleBOT
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fallow dust
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can somebody confirm my definitions:

obtuse pebbleBOT
fallow dust
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one to one: every y has at most one x

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onto: every y has at least one x

shadow dagger
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yeah they're fine

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crisp spruce
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I don't get how I'm supposed to calculate the average acceleration

obtuse pebbleBOT
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@crisp spruce Has your question been resolved?

severe pasture
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@crisp spruce Has your question been resolved?

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jagged isle
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hii

obtuse pebbleBOT
jagged isle
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I want to calculate the Eigenvector for the Eigenvalue λ = 3 of a matrix A \begin{bmatrix} 1 & -1 & 2 \ 0 & 3 & 3 \ 0 & 0 & 9 \end{bmatrix}.

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

jagged isle
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Right now I want to calculate Ker(A - λ!)

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But I am currently stuck, because I obtained a zero row

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Does that mean, that I can use any number for that variable??

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First I got \begin{bmatrix} -2 & -1 & 2 \ 0 & 0 & 3 \ 0 & 0 & 6 \end{bmatrix}.

warm shaleBOT
#

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

jagged isle
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And now I have \begin{bmatrix} -2 & -1 & 2 \ 0 & 0 & 3 \ 0 & 0 & 0 \end{bmatrix}

warm shaleBOT
#

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

unreal musk
jagged isle
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thanks !!

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!close

obtuse pebbleBOT
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@jagged isle Has your question been resolved?

steady venture
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bitter terrace
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does my solution to part b look ok

obtuse pebbleBOT
bitter terrace
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Also if a bases has 2 linearly independent elements we say it has 2 dimensions but what does the amount of elements in the basis tell us?

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for example W bases has 2 elements but the vector in the bases has 3 elements

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does that mean its a 2 dimensional space in a 3 dimensional space?

minor nova
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So yeah basically that

obtuse pebbleBOT
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bitter terrace
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Im allowed to say W is a sub space of R3 if it spans R3 right

gilded needle
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W is all of R^3, right?

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a vector space is a subspace of itself, so what you said is correct

bitter terrace
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Also idk if this a typo because I heard this book has tons of typo but he is interchangeably using basis and bases

gilded needle
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where do you see bases?

bitter terrace
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the reason its dimension 4 is because its bases has 4 elements?

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earlier he would use bases I believe to represent the set of basis vectors

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let me find it

gilded needle
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if used properly, "bases" is the plural of "basis"

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but to answer your question yea, if a basis (any basis) of a vector space has N vectors, then the vector space has dimension N

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(every basis of a given vector space has the same number of vectors)

bitter terrace
bitter terrace
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if im understanding right

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if a and b are vectors

gilded needle
bitter terrace
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oh ok

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so a, b are basis vectors of the basis {a,b}

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where a and b are linearly independent

gilded needle
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yea, assuming they actually form a basis

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(i.e. they are linearly independent and span the whole space)

bitter terrace
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span the whole space?

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so if I had

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a basis in R3

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ohhh

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the second part

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is saying that like

gilded needle
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you would need 3 linearly independent vectors

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in R^3

bitter terrace
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oh ok

gilded needle
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any 3 linearly independent vectors in R^3 are a basis of R^3

bitter terrace
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oh ok I see

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thanks for the clarification

obtuse pebbleBOT
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@bitter terrace Has your question been resolved?

obtuse pebbleBOT
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meager vapor
#

Hi

obtuse pebbleBOT
meager vapor
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I’m confused on how to do find the points to find the graph and the domain and range

stiff leaf
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Domain and range?

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Oh I gtg so can't help if you reply

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But domain is just every x point of the function and range is every y value

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Like in a x^2 function (-infinity, infinity) is the domain

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And (0,infinity) is the range

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Here in the piece wise function you use these brackets '-> [ when you have an equal to operator for a number

obtuse pebbleBOT
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@meager vapor Has your question been resolved?

meager vapor
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But I can’t seem to figure it out

obtuse pebbleBOT
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violet timber
obtuse pebbleBOT
violet timber
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Okay so I want to 4d

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I haven't done this since last year so I'm rusty but

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Do I find something that multiplies to -72 and adds? to -21

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I forgot if that's correct

obtuse pebbleBOT
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@violet timber Has your question been resolved?

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cloud ibex
#

. Caleb is trying to bake a pie for his grandma. The pie crust costs $6 and apples cost $3 per pound. He has $33 to spend.

a) Write an inequality to represent this scenario.

b) What is the most pounds of apples he can get

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how would i slove this???

obtuse pebbleBOT
unreal musk
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"he can't spend more money than he has..."

cloud ibex
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how would i write the inequality??

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i know minus the crust he has 27 to spend divide by three he can get 9 pounds of apples

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but how would i write that into a inequality??

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x3-6<33???

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3x*

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3x+6<33??

fathom light
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Yep

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He can spend all 33$ if he wants

cloud ibex
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ok thanks

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have a goodnight!!!blobsatisfied

fathom light
obtuse pebbleBOT
#

@cloud ibex Has your question been resolved?

cloud ibex
#

Yes

obtuse pebbleBOT
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heady turtle
#

"when finding extrema, it is important to consider saddle points along with local maxima and minima." Why? we already know that saddle point is not an extrema, isn't it? (since they are points where the function has critical points but they are neither local maxima nor minima) Then why should we consider it when finding extrema?

errant basin
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I think if its more like, when you find critical points, it falls into either local max/mins, but not all critical points are local max/mins but can be saddle points instead

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It might just be warning you to check your critical points and not jump to assumptions of solely max/min

heady turtle
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I mean like, if we want to find the extrema of a function, we need to check its interior critical points and boundary points, right?

errant basin
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yes

heady turtle
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And if we find that there's only a critical point in the interior which is saddle point

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Shouldn't we just ignore it cuz we shouldn't consider saddle point when finding the extrema

normal cairn
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from what i understand, thats exactly what your original message says. the way we find maxima is by finding the critical points first. but not all critical points are maxima or minima, so it's important to always keep in mind that any critical point we find could very well be a saddle point

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maybe im misunderstanding, but thats what i got

heady turtle
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Hmmm Actually I mean, uhh

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Mind that here local extrema and extrema are different

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Maybe I express the terms wrongly

heady turtle
normal cairn
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my only thought is that while you have in your mind two different steps: a) finding critical points and identifying them as maxima or minima and then b) picking the largest maxima to call the extrema.
maybe the sentence you're quoting doesn't discern those as two different steps, and simply puts all of the steps in one pile. in which case, while searching for the extrema, you would actually just have to identify the saddle points

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maybe its shaky wording on the sentence you quoted or something im not getting, but as far as im concerned youre absolutely right that if you already know all the maxima of a function as well as all the saddle points, then you dont really care about the saddle points, all you care about are the maxima and which one of them is actually the largest

heady turtle
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I made a summary, Just want to confirm : if we want to find the extrema of a function, we need to check its interior critical points and boundary points, but if we find that there's only a critical point in the interior which is saddle point, then we dont really care about the saddle points, right? all we care about are the maxima and which one of them is actually the largest, since the only point in the interior is a saddle point, so we only need to focus on the boundary points, am I understanding correctly? @normal cairn

obtuse pebbleBOT
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frail crater
#

How do i go about solving these proportions involving fractions, i can do it with decimals and whole numbers but I’m confused how to do this with fractions, do i need to make them all have the same denominator? Do i neeed to convert to decimals?

frail crater
wary trellis
#

2 1/2 can be written as 5/2
3 3/4 can be written as 15/4
9 1/2 is 19/2
So we know
5/2 : 15/4 = 9/2 : x
Aka 5* x/2 = 15* 9/8
Therefore x = 27/4 aka 6 3/4 boxes

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If my calculations arent off but that's the gist of it

frail crater
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the answer im getting on the answer sheet is 14 1/4 boxes

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but so you converted them to improper fractions, i will try that

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lets start over

wary trellis
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The idea is to find the amount of boxes per kg which you get from the fact that 2 1/2 kg fills 3 3/4
Which should be 5/2 => 15/4
To get 1kg of sugar we need to divide with 5/2
1kg => 3/2box
And then just multiply 3/2 boxes by 9 1/2

frail crater
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for example

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with this question using decimals

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i do this

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I use the cross method

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But with fractions I’m not sure how to do that

wary trellis
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Whenever you have Number.xyz
You can write it as Number xyz/1000

frail crater
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right because of the decimal places

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ok i understand that

wary trellis
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So for example 1.63 is 1 63/100

frail crater
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ok im following so far.. so how can we translate that to the question now, so for example 2 1/2 kg of sugar fills 3 3/4 boxes

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do we now make those numbers decimals?

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or how do i go about finding the ratio to solve for x

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like would that just be 2.5 and 3.75 can i do that or no

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ya so if i just convert all the fractions to decimals and solve it that way i was able to get 14.25 or in other words 14 1/4. ill try to just kep doing that

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thank you

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🙂

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.close

obtuse pebbleBOT
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sand meadow
#

Need help evaluating the definite integral

obtuse pebbleBOT
sand meadow
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I'll post screenshots of my solution

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I successfully integrated it but can't evaluate the limits

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It's leading to indeterminate forms, getting stuff like infinity - infinity

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on the first screenshot, the solution starts from the second Q. I made a mistake the first time

tardy epoch
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what

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why do you have 4 pages of work

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with half of it scribbled out

sand meadow
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I made mistakes. Let me rewrite it without the mistakes

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or is it even necessary? I'll just write the final answer

tardy epoch
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showing some work would be helpful if you make mistakes

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otherwise just use an online calculator

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,w int 0 to inf of x^(2018/3) / (x + x^2019)

sand meadow
#

I used it to confirm that I arrived at the correct integral

warm shaleBOT
sand meadow
#

I've seen the answer to the question, I just don't understand it

tardy epoch
#

surprising wolfram can't figure this out

sand meadow
#

I understand how to integrate, but the part where you evaluate the limts, how they arrived at the answer was weird

tardy epoch
#

show

sand meadow
#

a moment, it's calculating it again

#

damn, lol, It also couldn't solve. What i fed it the first time was the simplified version after I had done some manipulations

#

let me show my workings more neatly first

#

after simplifying, it becomes an integration by partial fractions question

#

use wolfram to evaluate this

obtuse pebbleBOT
#

@sand meadow Has your question been resolved?

tardy epoch
#

i lost you here. which term x^2019 become?

sand meadow
#

Full solution re-written

sand meadow
#

so it became x raised to 2018

#

and x raised to 2018 is u^3

#

it essentially simplifies to an integration by partial fraction question which I have solved, my issue is putting in infinity into the final answer

tardy epoch
#

okay assuming your antiderivative is correct

#

which i can't find

#

plugging in infinity is really taking a limit

sand meadow
#

its in the last pic, at the bottom

tardy epoch
#

$F(x) |^\y_0 = \lim_{B \to \y} F(B) - F(0)$

warm shaleBOT
#

riemann

sand meadow
sand meadow
tardy epoch
#

they're called improper integrals

sand meadow
#

in this case what would t be?

tardy epoch
sand meadow
sand meadow
tardy epoch
#

you could think that way yea

tardy epoch
sand meadow
#

oh the limit is for only f(b)?

#

this math problem is so annoying, how do i even take the limits of that? bleakkekw

#

Thats where my issue is

#

If i directly substitute infinity, i'd be getting indeterminate forms like infinity - infinity

#

do you know how they got the answer, that pi over stuff

tardy epoch
#

Use log identities to combine it into one log

#

,tex .log rules

warm shaleBOT
#

riemann

sand meadow
#

hmm

obtuse pebbleBOT
#

@sand meadow Has your question been resolved?

#
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night blaze
#

I got A. to 44.98cm But i cant figure question B out without using the derivative. Can somebody help

tawny copper
#

Well, u can graph it

#

Then said "Base on the graph" blah blah blah but actually use derivative to get the answer

night blaze
#

But I can’t

tawny copper
#

?

night blaze
#

“Without using the derivative”

tawny copper
#

Yeah

#

That why u graph it

night blaze
#

So I graph A(r)

tawny copper
#

Use derivative to get the actual value (on your note), then pretend to graph it and write "base on the graph the smallest possible.... is ....." on ur paper

night blaze
#

Yeah I know you can use it but the class with this question(my brothers class haven’t even learned derivatives yet😭

tawny copper
#

LMAO

night blaze
#

So I don’t understand how to solve it

#

How they solve it

tawny copper
#

Then graph it then

#

Very slow

#

But it works

night blaze
#

Can’t I use limit ?? Perhaps

#

X->0

#

Yeah I don’t know

#

Is it possible to solve without finding the derivative????

#

<@&286206848099549185>

obtuse pebbleBOT
#

@night blaze Has your question been resolved?

timid silo
#

@night blaze why dont u just take the A(r) and instead of formally deriving to minimise it, just write out the limit definition of derivative and argue that if lim A(r+h)-A(r)/h is 0 as h goes to 0, then r must be an extremum of A. So you're still deriving but using limits and from first principle

night blaze
tawny copper
#

Teach ur bro calc 1

#

LMAO

night blaze
#

Impossible

tawny copper
#

problem solved

night blaze
#

Bei they’re learning about quadratic polynomials

#

They haven’t even got to vector yet nor derivatives

tawny copper
#

Isn't there a way to get local max min in quadratic poly?

night blaze
#

-b/2a

tawny copper
#

Yeah

#

But 1/x aint quad poly

night blaze
#

Yeah that doesn’t work

tawny copper
#

Literally teach ur bro a little calc wont hurt

night blaze
#

But how is it solvable

tawny copper
wicked shadow
wicked shadow
night blaze
#

F’(x)=0

wicked shadow
night blaze
#

Nah

#

Just typing

tawny copper
#

teach ur bro graphing and fx diiference

night blaze
#

Brb

tawny copper
#

mono somthing table

wicked shadow
wicked shadow
tawny copper
#

Im dad

wicked shadow
tawny copper
#

U have my permission to laugh

wicked shadow
#

U need a doc.

#

U have been diagnosed as paranoia

wicked shadow
night blaze
#

On my language is called monotoni forhold

wicked shadow
#

What, this question cannot be solved then

night blaze
#

Yeah that was my thought lol

wicked shadow
night blaze
#

Monotoni?

elder ingot
#

1 + 1 = 3?

night blaze
#

Explaining how the graph looks based on the derivative

wicked shadow
night blaze
obtuse pebbleBOT
#

@night blaze Has your question been resolved?

wicked shadow
# night blaze Monotoni?

Now I see,
Look bro long story shorts
U brother need to learn calculus basics other than it he won't be able to anything

obtuse pebbleBOT
#
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glacial robin
#

Could someone send me in the right direction

light quarry
glacial robin
#

Wait, should i use the sum of identity angles for this

#

I really dont know where to start yeah

light quarry
#

So there are 2 formulas you need

#

1 is for the magnitude of complex numbers and the others is for the angle

glacial robin
#

Uhu

light quarry
#

And you either have those formulas and memorise them or you can see and derive them from drawing z in the complex plane

glacial robin
#

What are the formulas?

light quarry
#

So if $z = x+yi$ then the magnitude is $|z| = \sqrt{x^2+y^2}$ and $tan(\theta) = \frac{b}{a}$ but for the tangent you have to check if the solution is in the right quadrant

warm shaleBOT
glacial robin
#

Do i need the tangent tho?

light quarry
#

Oops I didn't even realise I put b/a it should be y/x

glacial robin
#

All good

light quarry
glacial robin
#

Theres a formula for the tangent but for this tangent it does not seem like i need the tangent

light quarry
#

I mean this formula just calculates the angle easily

glacial robin
#

Okay

#

I have no idea how to use the formula

light quarry
#

Ok so here we have that x = -5 and y = -5 right

glacial robin
#

Yes

light quarry
#

So plugging into the formula you get $|z| = \sqrt{(-5)^2+(-5)^2} = 5\sqrt{2}$

warm shaleBOT
light quarry
#

That's the first part

glacial robin
#

Huh

#

So 50 is 5sqrt2?

light quarry
#

Yep

glacial robin
#

Oh

#

I see

#

Okay

light quarry
#

$\sqrt{50} = \sqrt{252} = \sqrt{25}\sqrt{2} = 5\sqrt{2}$

warm shaleBOT
glacial robin
#

What have i exactly calculated now

light quarry
#

Now we get that $tan(\theta) = 1$ meaning that $\theta = \frac{\pi}{4}$ but if we look at the complex plane that's the wrong quandrant so we can add $\pi$ for the final solution of $\theta = \frac{5\pi}{4}$

warm shaleBOT
light quarry
#

That is in radians

#

But I see that your solution asks for degrees so that would be $\theta = 45deg$ for the first part and adding 180deg to get $\theta = 225deg$

warm shaleBOT
glacial robin
#

Okay

#

What exactly is the format in which im answering

#

Because it seems kind of weird

light quarry
#

It seems to be degrees so you would get $z = 5\sqrt{2}(cos(225)+i*sin(225))$

warm shaleBOT
glacial robin
#

Yeah but why do i have to put those numbers in that order

#

I know the solution but i dont get why thats a solution

light quarry
#

I am not sure what you're asking about

#

The formulas we used to derive the solution?

glacial robin
#

Yes

#

Why do those work

light quarry
#

If you draw out a complex number like this

glacial robin
#

Sorry, i get taught in a different language then i answer questions in so it all confuses me

light quarry
#

r or the magnitude or |z| we get from pythagorean theorem

#

And the angle theta by the fact that it's a right triangle and that's just the definition of tan

glacial robin
#

Alright, thanks

#

Have a good day

#

.close

obtuse pebbleBOT
#
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violet stream
obtuse pebbleBOT
violet stream
#

I have to use integration by parts

#

this is my work so far

tardy epoch
#

!ss

obtuse pebbleBOT
#

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violet stream
#

I figured it out

#

.close

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dapper patrol
#

i need help i cant solve this math question…

dapper patrol
#

<@&286206848099549185>

cold yacht
#

what part are you struggling with?

dapper patrol
#

im confused on how to draw the function graphs my teacher wasn’t good at explaining this lesson

cold yacht
#

do you know what type of function a would create? parabola, linear, etcc

dapper patrol
#

a quadratic

cold yacht
#

yes !!

fallen igloo
#

a quadratic function is the same as a parabola

cold yacht
#

since 5x^2 is a quadratic equation, it will graph a parabola. what does the coefficient x^2 tell you about how the parabola will be shaped?

#

will it be upwards or downards?

dapper patrol
#

it would have a minimum

#

so downwards

cold yacht
#

close - a minimum would mean a U shape, so upwards

fallen igloo
#

If the x² of the equation is positive, the parabola would be upwards

cold yacht
#

can you identify where the vertex/atix of symmetry would be?

dapper patrol
#

would it be at 2,0?

cold yacht
#

the vertex?

dapper patrol
#

wait wouldn’t it start at 0?

cold yacht
#

or the axis of symmetry

dapper patrol
#

the vertex

cold yacht
#

in the formula, ax^2 + bx + c, bx denotes where the vertex would be

#

snce there is no x term or constant in our equation (its just 2x^2!), it would start at (0,0)

dapper patrol
#

because the answer for 4a) is this and im confused

cold yacht
#

see how the minimum point is at (0,0)?

dapper patrol
#

yeah

#

how would i determine where they are drawn on the graph?

cold yacht
#

where the vertex is drawn, or the lines pointing up to infinity?

dapper patrol
#

lines on the graph

cold yacht
#

for the second part, you can start plugging in points into your equation

#

its easy to start with x=-2, x=-1, x=0, x=1, x=2

#

once youve found the correct x value, you can plug it back into your function to find the corresponding y

#

can you try for -2 first?

dapper patrol
#

would it be 1?

cold yacht
#

so 2(-2)^2 = 20

dapper patrol
#

ohhh

cold yacht
#

so the point would be (x,y) = (-2, 20)

#

does that make sense ?

dapper patrol
#

but on the graph both equations start at 0 and dont go up as high as 20

cold yacht
#

well, they do, you just cant see it because the graph has been constrained to show only up to y= 10

#

in reality, those lines would go up forever

#

thats what the -> arrow shows at the end, that it continues on to infinity

dapper patrol
#

ohh so the graph is just showing a representation of what it would look like instead of including all the exact points

cold yacht
#

oh wait im looking at the wrong equation btw

#

urs is 2x^2 not 5x^2

#

so it would be 2(-2)^2

#

which is 8

#

and u can see on the graph it does intersect at y = -2, x = 8

#

sry for the confusion im in an 8am class 😢

dapper patrol
#

ohh its ojay😞

cold yacht
#

try with -1

dapper patrol
#

wait i have a question first

cold yacht
#

if the graph is correct, itll intersect at y =1

#

2*

#

i cannot read

dapper patrol
#

the substitution is always used to get the points of a function right?

cold yacht
#

yes, to get the y value

#

since you are plugging in random x values

dapper patrol
#

ohh okay , so even if it wont reach the point i can just draw the arrows

cold yacht
#

yeah, thats why its a good idea to kind of play around with the substition, and also just be reasonable

#

you could find x = 100

#

but its not going to really be easy to show the scale of the graph that way

#

thats why -2 to 2 mightbe easiest, like theyve shown

dapper patrol
#

ohh okay

#

yeah my teacher said to use these for the functions (i’ll send it in a second

cold yacht
#

yep, you can see how your teacher has chosen a x value, and then plugged into the formula right?

#

to get y?

dapper patrol
#

i just wasn’t sure how to completely use them

#

yeah

cold yacht
dapper patrol
#

yeah because he didn’t specify well on how to plot the graphs

cold yacht
#

well, from the values, you can kind of see how it would look just by kind of playing connect the dots

#

you can put the values found on a graph, for instance for sqrt(x)

#

(0, 0) (1,1) (4,2) (9,3)

#

and kind of see what its going to draw

dapper patrol
#

ohhh okayok

cold yacht
#

also, it may be more fun to use a graphing software such as desmos

#

to just plug in thos ebasic equations on the board,

#

and play with changing it

#

like what happens if you change x^2 to 5x^2? what about -5x^2?

#

same with the others

dapper patrol
#

oooo yes

#

thank you so much this was very helpful im so thankful😭😭🙏🙏🙏

cold yacht
#

nws catthumbsup catthumbsup i hope its a bit clearer for u now

dapper patrol
#

i have my test tomorrow so i have to review most of the styff im confused about

#

yes it did thank youu!!

obtuse pebbleBOT
#

@dapper patrol Has your question been resolved?

obtuse pebbleBOT
#
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spare prairie
#

Not sure what to do now that I solved for X?

obtuse pebbleBOT
spare prairie
#

Find the points of inner section

sturdy arch
obtuse pebbleBOT
#

@spare prairie Has your question been resolved?

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frigid oyster
#

Intro to diff eq

Looking to solve y' + 2yx = e^{-y^2}

I've thought about using a substitution of v = y^2 which would yield the v' = 2yy' but i don't think it is quite right because of that other y'. Thoughts?

obtuse pebbleBOT
#

@frigid oyster Has your question been resolved?

frigid oyster
#

<@&286206848099549185>

wary badger
frigid oyster
#

i think its like, an impossible human solve

#

but maybe im just delusional

wary badger
#

that says dx/dy sir

frigid oyster
#

bruh

#

thanks i got it from here then 💀

wary badger
#

as far as i know

frigid oyster
#

ok that is why i was going crazy lol

#

yeah i didnt see a way to solve it

#

.close

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boreal palm
obtuse pebbleBOT
boreal palm
#

can someone explain what i did wrong here bc idk why the answer key got y/2sqrtxy

#

and i got just y

restive gorge
boreal palm
#

oops i js figured it out

#

i forgot parentheses and so forgot to do a step

#

but can u explain where to start with a diff problem

restive gorge
#

sure

boreal palm
#

idk what im doing

restive gorge
#

what do you wanna do

#

implicit differentiation?

boreal palm
#

find dy/dx

#

yeah

restive gorge
#

ok

#

you apply 1st line d/dx ( ) on both sides

heady turtle
#

Looks good

boreal palm
warm shaleBOT
restive gorge
#

Let's start with sine

boreal palm
#

cosx + -2sin2dy/dx = 0?

restive gorge
#

ok you boss

#

yea

warm shaleBOT
restive gorge
#

now solve for y'

boreal palm
#

oh

warm shaleBOT
restive gorge
#

last step?

boreal palm
#

just isolate the dy/dx and divide cosx/4sin2y?

#

wait

restive gorge
#

yea

#

that's it

boreal palm
#

why is it sin2y and not sin2dy/dx?

warm shaleBOT
restive gorge
#

It's like doing

#

f'(g(x)) = f'(g'(x))

#

this is wrong

boreal palm
#

ohhh

restive gorge
#

Chain rule was

#

f'(g(x)) = f'(g) * g'(x)

boreal palm
#

i gotchu

restive gorge
#

thanks

boreal palm
#

thank you sm!

#

.close

obtuse pebbleBOT
#
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normal inlet
obtuse pebbleBOT
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To ask for mathematics help on this server, please open your own help channel or help thread. See #❓how-to-get-help for instructions.

obtuse pebbleBOT
normal inlet
#

I don’t understand the jump from sinx+ to sinx()

raw egret
#

factor out sinx

#

look that, 1+cot^2x is a trig identity

normal inlet
#

so i divided everything by sin x

raw egret
#

it's like this problem:

4x + 7xh + 9xc

factor out the x in this problem

#

x(4 + 7h + 9c)

#

bc

#

x * 4 + 7h * c + 9c * x = 4x + 7xh + 9xc

#

and yeah, $\frac{sinx}{sinx} = 1$

warm shaleBOT
#

tank_driver011

normal inlet
#

i think i get it because the sin infront of the cot turns into 1 making it just cot

raw egret
#

exactly bc sinx(1 + cot^x) is the same as the original which is sinx + sinxcot^x

#

when you're ever in doubt, just multiply it out

normal inlet
#

how is the cot untouched from the factor out

raw egret
#

i don't understand.

normal inlet
#

when i divided the sin infront of the cot its 1 but do i not divide cot by sin as well

raw egret
#

think of it, like, taking the stuff out that repeats. the stuff that repeats, you can separate the equation to 'divide' it out

normal inlet
#

okay

raw egret
#

@normal inlet better?

normal inlet
#

yeah yeah

#

i get it now

raw egret
#

great

#

also, sinx = 1/cscx

#

that's how they got csc^2x/cscx

normal inlet
#

.close

obtuse pebbleBOT
#
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tropic mirage
obtuse pebbleBOT
tropic mirage
#

Can I have help solving this problem

#

I don't think it's solvable

teal turret
#

is everything except p1 a constant?

#

@tropic mirage

tropic mirage
#

there are n goods

#

idk if you know economics or langrange

teal turret
#

ok can u answer my question lol

tropic mirage
#

but the utility function was
(sqrt(x1)) + a2(sqrt x2) + ... + an(sqrt xn)

#

uh

#

pn are various prices

teal turret
#

but are all the variables shown above independent of p1?

tropic mirage
#

yes

teal turret
#

ok so what makes u think its unsolvable

#

wanna work thru it?

tropic mirage
#

because mathway says it's so

#

the equation looks horrendous

teal turret
#

its not that bad

tropic mirage
#

I might've came to the wrong conclusion

teal turret
#

do u wanna do it?

tropic mirage
#

yes

teal turret
#

ok so just do what i tell u

#

first, in that big clump of parentheses on the left

#

just distribute everything

#

lmk what u get

tropic mirage
#

p1pn^2 + p1^2pn a^2

#

times u^2

teal turret
#

good

#

and distributing in the u^2 we get?

tropic mirage
#

u^2 times both pluses

teal turret
#

ok, let me write in latex

#

$p_1 \cdot u^2 p_n ^2 + p_1 ^2 \cdot p_n a^2 u^2$

warm shaleBOT
teal turret
#

do u agree?

tropic mirage
#

yup

#

and divided by pn^2 + a(subscript n) m p1^2 a^2

teal turret
#

ok before we move on to the second group

#

im gonna make life a little easier

#

$x = u^2 p_n ^2 \newline y = p_n a^2 u^2 \newline z = p_n ^2 \newline t = a_n ma^2$

#

so we get

warm shaleBOT
teal turret
#

yes?

tropic mirage
#

one second

#

let me process

#

yes

teal turret
#

ok, now moving onto the second group, let me make a few more constants

warm shaleBOT
tropic mirage
#

so xp1 + yp1^2 / z+t?

#

oh

#

t*p1^2

teal turret
#

$\frac {xp_1 + yp_1 ^2}{z + tp_1 ^2}$

warm shaleBOT
teal turret
#

agree?

tropic mirage
#

yes

teal turret
#

ok so now heres ur choice

#

quotient rule or product rule

tropic mirage
#

quotient? becuase it's a fraction

teal turret
#

we could use product, but since u chose quotient, we'll do that

tropic mirage
#

x+yp1^2 - xp1+2yp1 / (z+tp1^2)^2?

teal turret
#

no

#

do u remember the formula for quotient rule

tropic mirage
#

f'g - fg' / g(x)^2

#

oh

teal turret
#

the top is f and the bottom is g?

#

yes ok

tropic mirage
#

(x+2yp1) (g) - (f) 2p1t / (g)^2

teal turret
#

x+2y is incorrect

#

there u go

tropic mirage
#

is that it

teal turret
#

u have a + in the middle

tropic mirage
#

oh

teal turret
#

also, its not 2p1

#

good

#

correct now

#

now let me put that in latex

tropic mirage
#

Can you stay with me for a second? I need to do Pn but I think I can simplify constants and figure it out

teal turret
#

$\frac {(p_n ^2 + a_n ma^2 p_1 ^2)( u^2 p_n ^2 +2 p_n a^2 u^2 p_1) - ( u^2 p_n ^2 p_1 + p_n a^2 u^2 p_1 ^2)(2a_n ma^2 p_1)}{(p_n ^2 + a_n ma^2 p_1 ^2)^2}$

#

do you agree with this?

tropic mirage
#

1 second

#

yes

#

i think I can do pn

#

one second

warm shaleBOT
teal turret
#

theres ur derivative

tropic mirage
#

Pn^2 x + Pn y / Pn^2 + z

#

I didn't expand it

#

thank you though

teal turret
#

well u cant exactly use x,y,z because they include p_n in them

#

u have to create new constants

tropic mirage
#

(2Pnx + y)*g - f (2Pn) / g^2

#

i did that\

#

x= u^2 P1, y= P1^2a^2u^2, z=anmp1^2a^2

#

so it becomes

#

Pn^2(x) + Pn(y) / Pn^2 + z

teal turret
#

i dont rlly feel like checking that lol, but if u feel u got the idea, then thats good

tropic mirage
#

well this has been fun

#

the equation looked impossible

teal turret
#

if its just a ton of constants, its not a big deal

#

just make new ones that are made up of the old ones

#

what exactly are u doing with this

#

ik u mentioned econ

tropic mirage
#

oh

#

again idk if you know constrained optimization

#

we have a utility function subject to a constraint

#

find the marshillian demand

#

plug back into utility function to get indirect utility

#

set that equal to u, solve for m, which gives expenditure function

#

divide by p1 and pn to get hicksian demands

#

which is what I just did

#

(2Pn(x) + y) (Pn^2 +z) - (Pn^2*x + Pny) (2Pn) / g^2

obtuse pebbleBOT
#

@tropic mirage Has your question been resolved?

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heady turtle
#

A plane figure of infinite area rotated around an axis always produces a solid of revolution of infinite volume?

I'm not even sure if I understand this statement, can anyone give me an example

worn yoke
#

consider the region between the $x$ axis and some function $y = f(x)$, $x \ge a$. then we could find the area using an improper integral [ \int_a^\infty f(x) \odif x ] the area may be infinite if the integral diverges. but we can also rotate it about the $x$ axis, which using the disk method would produce a solid of volume [ \pi \int_a^\infty [f(x)]^2 \odif x ]
the volume may be infinite if this integral diverges

warm shaleBOT
heady turtle
#

Should depends on whether it's diverging or not?

worn yoke
#

well the area is infinite if the first integral diverges, and the volume is infinite if the second integral diverges. the question is, does the first integral diverging necessarily mean the second integral diverges?

heady turtle
#

So the statement is correct?

worn yoke
#

is it? does the improper integral of f(x) being divergent imply that the improper integral of [f(x)]^2 is divergent?

heady turtle
#

No

worn yoke
#

that function is not riemann integrable

#

neither of those would converge

heady turtle
#

Ooh right

#

Lemme rethink

#

Umm how can I come up with such a counterexample

worn yoke
#

do you know any families of functions whose improper integral convergence depends on the power?

heady turtle
#

Wait no

worn yoke
#

you were on the right track there

heady turtle
#

Ok yes 1/x^p

#

P>1 & P<=1

#

So 1/x &1/x²

#

Does this example work? @worn yoke blobsweat

worn yoke
#

both of those diverge

heady turtle
#

Edited edited

#

Not familiar with series knowledges😭

worn yoke
#

we want one of them to be the square of the other

heady turtle
#

I think this works now

#

Thank you

#

.close

obtuse pebbleBOT
#
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obtuse pebbleBOT
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spring fossil
obtuse pebbleBOT
spring fossil
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.close

obtuse pebbleBOT
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next widget
#

Is b right?

obtuse pebbleBOT
#

@next widget Has your question been resolved?

obtuse pebbleBOT
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timid silo
obtuse pebbleBOT
timid silo
next widget
obtuse pebbleBOT
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@karmic flare Has your question been resolved?

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cold brook
#

is there a trig identity for A cos(b) + B cos(a)?

kind hawk
#

I think there was some sort of trick if you divide it by A^2+B^2. but I dont quite remember it

#

the idea being that the new coefficients x,y then satisfy x^2+y^2=1 and then other trig shenanigans

obtuse pebbleBOT
#

@cold brook Has your question been resolved?

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spring fossil
obtuse pebbleBOT
spring fossil
#

Hello

#

I have no idea how to complete this. Thank you

ruby path
#

divide the top and bottom by t

obtuse pebbleBOT
#

@spring fossil Has your question been resolved?

spring fossil
#

.close

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proven narwhal
#

Good night from southeast asia, i need some tips, today i feel bad when i already put my effort to learn matrix gauss, gauss jordan and cremer method for linear equation, i understand the stuff about determinant and adjacent Transpose but the thing is the teacher give me the question with big and fractional number without calculator for limited time it's just too hard, so i wanna know is this normal i struggle with this? Even though i really understand the theory of it? How can i improve this?

obtuse pebbleBOT
#

@proven narwhal Has your question been resolved?

obtuse pebbleBOT
#

@proven narwhal Has your question been resolved?

gentle steeple
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heady turtle
#

how can I turn it into a triangle matrix....I'm so hopelessly silly, cant find a way out

wary badger
#

upper? lower?

heady turtle
#

upper

kind hawk
#

did A already include the t?

#

otherwise you arent supposed to have t in the off diagonal

#

is this still for computing the determinant?

heady turtle
#

yes

kind hawk
#

then dont do it

#

use block matrices

heady turtle
#

They said

#

10 SECS

#

I TOOK 10 HOURS

#

I'm indeed hopelessly silly I might just turn into a potato

kind hawk
#

no clue who they are and what they meant. but block matrices are way easier here imo

wary badger
#

wouldn’t the trick be LU decomposition

kind hawk
#

LU is ref but more fancy

timid silo
#

u can and every column to the first one and u get 1-t or 0 in all the forst column

#

and u factorise

heady turtle
heady turtle
heady turtle
timid silo
#

nono just do R1<-R1+R2
R1<-R1+R3 etc

kind hawk
#

its not like that magically solves it

timid silo
#

hmm it does tho

kind hawk
#

also should probably write C's if you want columns and not rows

timid silo
#

idk im not english

heady turtle
#

wait It doesn't work😇

heady turtle
kind hawk
#

thanks. are you now gonna try block matrices?

heady turtle
#

Am I partition correctly? @kind hawk

#

seems wrongcat_happycry

kind hawk
#

its not wrong, just not helpful

#

you want to partition it in a way such that at least one of the blocks is just zero

#

and the two blocks on the diagonal are square

heady turtle
kind hawk
#

yes

#

and then you can partition the smaller blocks again

heady turtle
#

darn now it seems much simplercat_happycry

kind hawk
#

yes

heady turtle
#

[
det = \left[ (-t\left(\frac{6}{7} - t\right) - \frac{6}{49})(\frac{1}{7}-t) \right] \left[ -t\left(\frac{6}{7} - t\right) - \frac{6}{49} \right] (1 - t)] = 0
]

#

@kind hawk Am i doing rightblobsweat

kind hawk
#

yes

#

dont multiply out everything

heady turtle
#

[ -t\left(\frac{6}{7} - t\right) = -t \cdot \frac{6}{7} + t^2 = -\frac{6t}{7} + t^2 ]
[-\frac{6t}{7} + t^2 - \frac{6}{49} ]

warm shaleBOT
heady turtle
#

Darm this root doesn't looks good

#

Might including some irrational stuff

#

@kind hawk This ugly root is also included, right

#

Except x=1, 1/7

#

It has 3 roots in total

kind hawk
#

yes

#

well, two extra roots

heady turtle
#

Extra roots?

#

Anyway thanks

kind hawk
#

its a quadratic

heady turtle
#

.close

obtuse pebbleBOT
#
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kind hawk
#

two roots

heady turtle
kind hawk
#

.reopen

obtuse pebbleBOT
#

kind hawk
#

its 4 roots and two of those are double roots

#

you dont know what the min poly is yet

#

but it also has the 4 roots, the multiplicity might be different

timid silo
heady turtle
#

I think I get your meaning

#

Thanks

timid silo
heady turtle
#

.close

obtuse pebbleBOT
#
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heady turtle
timid silo
#

if its a- ti then the question is short if you want triangular matrix of a

timid silo
heady turtle
#

Hmmm i guess no

#

You should open another channel

#

Otherwise I can't open new channel myself