#help-23
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I have a problem as follows: 2x^2+kx+3=0, solve for k while k is a constant above 0. I believe that this is impossible if k has to be positive
factor it out and see
2(x+3)(x+1/2)=0 has solutions at x = -3 and x = -1/2 and a k > 0.
!nosols
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
how did you get helpful without learning that
this isnt a solution as the example asks for "solve for k", its just a counterexample for the "believe" of the op.
he/she has still to solve the example for himself/herself.
stop playing block captain
I think helpful is automatic anyways
wdym automatic
you still have to help a lot
I think I remember one of the mods saying it's a certain secret condition that the bot can automatically verify
I won't pretend to have a clue as to what the criterion could be
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You can do this?!?
This is allowed??
How does he set them equal to each other, why does that work? Huh
Yep it's allowed
You can rewrite exponents
$(\sqrt{a})^b = (a^{\frac 12})^b = a^{\frac b2}$
VulcanOne
How many laws/rules should I make sure I know for something like the SAT how many of those exist up to precalculus
Understand the general rules
woah interesting I didn't know that worked
Don't memorize anything
so the b distributes into the exponent?
Yep
yeah I wanna understand all the rules but i want a list so i can make sure id know all of them 😂
lol
anyway yeah cuz like ik general rules but then when i get given complex or tricky problems i just lose sense of them
@neat kiln ah you deleted your message. Okay.
cuz we barely use a lot of the fundamental rules half the time
at least not in creative ways and stuff
but i wish i used rules more to simplify math and be able to do a lot more stuff in my head and stop relying on technology
You need a lot of experience to be able to get creative
Lemme ask you a question nino
go ahead
Do you call your parents by their name?
What
What question is that
Then why don't you forget their name since you rarely use them
because other people call them their name idk?
it's also family and like
kinda different
i understand what u mean
That's why fundamentals of math is very important, treat it as you treat your family, you never know
i just wanna either find weird complex problems to work with to test and create more algebraic intuition or understand everything fundamentally
since most things are intuitive when it's a weird or tricky problems it throws that out the window and stops making sense
Try reading principa mathematica 💀
omg that is actually such a good idea
but there's probably better ways to learn calc 💀
Most tricky problems need a small piece of information to change it
Then it becomes familiar
right
i wanna find ways to work on those things
but im not ever exposed to them nor know about the roles i don't know about
if i did then id know xD
Well the best way is to play around with the rules yourself
yeah i thought so but what about the ones i just don't think about and might forget
I'd say to have a math expert give you a problem and you try poking it with what you know
Where can I find a math expert 💀
Usually your teachers are a good source
I wish all experts of every field were easily accesible and they could just help but like
nahh it's uncomfortableeee
Mood
yeah XD
Second would be the internet.
mhm that's why im here
You could search for hard SAT problems and the way they get solved
Also the books you have for math should be sufficient too
ehhh most problems in both of those sources aren't crazy
I'd say only math competition problems are usually crazy
cuz im in mu alpha theta and yeah those are hard
Math competition questions are really hard and they usually need actual math experts
i mean there's this guy which works with like more complex simple numbers and actually helps quite a bit
Check out the main channel @polymathematic !
Today's suspiciously nice mental math calculation is an example of a factoring pattern called the difference of two squares (or sometimes just the difference of squares).
Subscribe: https://bit.ly/polymathematic | Enable ALL push notifications 🔔
This pattern, or identity, is a² – b² = (a – b)(a +...
Well some stuff gets easily recognizable from the amount of times you worked on them
but yeah it's too time consuming to try to find resources so i don't ever know how to find things that rlly help me and don't take all my time looking for stuff
to a certain degree of competition math
I’m talking about high school comp math
late aime and above isn’t necessarily fundamentally simple lol
late aime?
You know amc10? If you score well enough you qualify for aime, then you can qualify for usajmo, etc
ah cool
yeah ive only done stuff in regional level, we could also go to states but it's expensive
there's different levels like algebra 1 algebra 2 precalc stats and calc
Does the school not pay for you?
not for states ;(
but yeah idk how to prepare and increase my intuition with all this stuff
like i wish i could solve logs in my head and stuff and simplify things easily to work with complex problems and use calculators less
how do you prepare for it?
for what
the exam
mu alpha theta? I recommend past exams. Really, for any math competition doing past exams and doing corrections is going to help you improve a lot.
yeahhh for the most part
i still struggle with dumb things sometimes i rlly just wanna get better with my intuition
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Thanks to Samuel for the suggestion! This is from a book of Olympiad problems by SilverZone. #math #maths #mathematics #shorts
Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1
Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas!
If you purchase through these li...
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@royal arch Has your question been resolved?
those are the quadrants
and they indicate positive or negative
so like cos is inverse is positive in quadrant 1
but negative in quadrant 2
what about quadrants 3 and 4?
cos is x
so x is positive in quadrant 1 and 4
negative in quadrant 2 and 3
but since the bounds are being set from 0 to pi
it's only focusing on those 2 quadrants
sin inverse is focusing on quadrants 1 and 4 because you have +90 degrees and -90 degrees
or in this case +pi/2 and -pi/2 since it's in radians
oh its just for x
than whats the difference between tanx cosx and sinx
what about tan
ah yes
so like... why are these "bounds" being shown
ok so right after these notes these are the example problems
just pretend the work and answers isnt there, like for example on a), why are we adding 26.7 to 180, and how do we know not to just subtract it from 270
I see
you always start from quadrant 1 and go counter clockwise
from quadrant 1 to quadrant 2 there is 180 degrees
yes yes yes i know othat
okay so to find your theta, you know it's gonna be 180+x
now you need to find x
since your sin (y value) is -0.45, you can inverse it and that's where the 26.7 comes in
ok this sounds dumb but like
lets take example d
what if instead of cos
it was sin or tan
what would the difference be
lets just say sin
arcsin(0.82) and then you add it to 180
wait i think im understandin where im trippin
theta isnt always the reference angle, correct?
i notice that on each example theres theta, and theres theta prime
theta prime is theta inverse
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if a graph is being transformed from ln (x+4) to ln (2x+4)
is that a stretch?
,w graph ln(x+4), ln(2x+4)
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can i get help with c
ik K=Kern(phi), where phi is the homomorphism from G to Sym(G/H)
K={g| g(aH)=aH for all (aH) in G/H}
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i dont really need help, im just wondering if theres a place where i can find tasks that a 15/16 year old can do at home to get better at math and things i should learn before studying for engineering
khan academy
Includes articles videos and is in lots of languages
at what stage is a normal 15/16 year old?
When you click on courses, pick something from high school section
Algebra 1 e.g.
The Algebra 1 course, often taught in the 9th grade, covers Linear equations, inequalities, functions, and graphs; Systems of equations and inequalities; Extension of the concept of a function; Exponential models; and Quadratic equations, functions, and graphs. Khan Academy's Algebra 1 course is built to deliver a comprehensive, illuminating, en...
You can then try course challenge
right, thank you
how far does this go
does it go to a level you have when studying for engineering?
Well it goes far enough to take you 2 months
I am not sure what level you need to study engineering
right okay
It covers whole high school + some slightly more advanced topics
right ill give it a try, thank you
when doing engineering you will have to do calculus 1 and 2 which is also in khan academy
great
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Could someone help me to prove this
Theorem: Suppose that f and g are analytic on A, where A is subset of ₵ is an openset.
Prove a f + b g is analytic on A
use the definition of analytic
this is different to your original question, right?
but looks fine
if f and g is an analytic function then f and g are differentiable functions
I tried to show that
the original question is to show that they are analytic, not differentiable
analytic => differentiable, but converse is not nessesarily true
Could you show that for me
show what?
this should be a standard result in your notes
if f and g are analytic functions, could you show that af+bg is also analytic function
whats your definition of analytic?
An analytic function is a complex-valued function that is defined on an open set in the complex plane and is differentiable at every point in that set. In other words, an analytic function is a function that has a well-defined derivative at every point in its domain.
are you sure
np
.close
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Hi does anyone know how to walk me through this
im having some trouble with these types of questions
nvm
.close
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now you should be able to do the rest
@fossil vine Has your question been resolved?
how did u get those numbers tho
CCC = something divisible by 111 -> Cx111.
ABAB = AB*101
wait why 101
ABAB=AB00+AB=ABx100+AB=ABx101
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I need some help on an easy mechanics question pls
Mass of a cyclist and his bike is 140kg. He's going along a straight road experiencing resistitive force of 50N. Find the work done when he goes from 6ms^-1 to 9ms^-1, travelling 30m
I get 2 different answers
I can't use F(distance) here can i?
Do I have to use ½mv²-½mu²
why can't you use F dot distance
you just need to know the right F lol
it's not like these definitions magically don't hold in special situations
because force changes depending on speed no?
I mean sure, it can
what F did you use?
why 1332 N
Then take off 50
so you just multiplied a bunch of shit together
so 1322
and hoped that it would work
yeah you need to review
like
force diagrams and all that
you're just multiplying random things
How is force due to gravity not mass x acceleration
the force due to gravity is the guy's weight
Yeah
what does that have at all to do with the situation here?
he's not accelerating downward
the road is pushing up and keeping him from falling through the planet
but depending on his weight it'll be more work done no?
uh not really
I mean sure, but that's only because weight is positively correlated with mass
but it has very little to do with weight
So why is F(D) wrong with F of 1322
because you just randomly multiplied stuff?
it's like asking why 100x100x10 is wrong
why would you expect it to be right
that's the real question
why would it be
Bc more weight?
why does the value of the gravitational field matter
it's not like gravity is pulling the guy backward
Idfk
I know I use ½mv²-½mu² now
you can use this
stop memorizing procedures and formulae
set up some equations involving energy and work
also learn the proper definitions of work and energy
My hw is on energy work and power lol
;-;
work is defined as F dot d
Yes...
you should get the same energy value if you use consv of energy or F=ma ^^
yeah so you can see that the force of gravity is downward while the distance traveled is horizontal
so how is gravity doing any work on the person
what would this be equal to ?
3100J
sorry I mean the relationship
in general
what are you actually working out
if you have 1/2mv^2 - 1/2mu^2 = ?
work done by a biker as he accelerates from u to v between distance s
u is 6
v is 9
s is 30
right, however there is a resistive force here
Yeah*
so it does calculate the work energy Fs but we have a resistive force R so it would be more (F-R)s
we calculate Fs
Rs would be the work done by the resistive force over the integral from a->b
It would indeed
wdym relationship
without the putting in the numbers
im sorry im lost what you mean
Wdym relationship
Relationship is like Fαx for spring extension in my country
ok
fαx=>f=kx
anyway
I'll assume u mean equations tho?
it doesn't matter.
so Fs-50s=½mv²-½mu²
yes it is quite a simple problem
30F=½(140(9²))-½(140(6²))-150
The following error occured while calculating:
Error: Syntax error in part "½(140(9²))-½(140(6²))-150" (char 1)
,calc 1/2 * (140(9^2))-1/2 * (140(6^2))-150
Result:
3000
huh
uh disgusting syntax problems
also it should be + Rs
not minus
which gets me 4650J
,calc 1/2 * 140 * 9^2 - 1/2 * 140 * 6^2 + 50 * 30
Result:
4650
For this problem? That is wrong
$\sum F = ma$
Clarkie
$F_{\rightarrow}-F_{\leftarrow}=ma$
Clarkie
$F{\rightarrow}=ma+F{\leftarrow}$ so presumably the forward force must increase if our motion periods remain constant, aka the cyclist must push harder to across a larger resistance
Clarkie
I mean think of it as cycling across sticky stuff that is resistive versus a nice smooth road ig
gotta put more effort in if you wanna travel the same distance across the same period
you could post it
this is quite literally the same principles
but we don't know F or s
why
But now I'm being told its all wrong
confusion is the most uncomfortable pain
understandable
it helps me to talk over with my profs or teachers with this stuff
if im ever in a pit of confusion
I would recommend doing the same.
Especially if you've been told that a must be some value
but hiding the formula behind abstraction generated by levels of 'this must be this value' is pretty painful
I'm just autistic as fuck and absolutely hate not understanding it
that is consistent throughout all of academia 
best to get familiar with the feeling now
Genuinely rn i feel like I could cry
I've taken hours
To do 2 questions
yep
and the worst part, nobody cares
To do 10 questions
mhm
this is brilliant later on btw
just recently spent three weekends on a problem and once you solve it the feeling is very addictive
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Can anyone help explain this to me?
I tried finding the lengths of the triangle to find the ratios
But the points aren't in exact spots
@frigid plinth Has your question been resolved?
@frigid plinth Has your question been resolved?
It's a practice test
I need explaining please
The guy above didn't even give an explanation
<@&286206848099549185>
Guy above didn't even help he just posted his friend's yt chnl and advertjsed
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kheerii
Why do I need to know it
I mean method 1 is literally doing method 2 just not showing it
I like method one
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x-15+1/2x
For some context in trying to add the length of to rectangles
wdym
lemme send a pic
3/2x - 15 would be ur answer
u said ur just adding them?
well I need to get the area of both rectangles combined so I need the length of both of them
it’s just Area = length x width
yep
why?
so if I have two other those on top of eachother
it’s just that the opposite sides are = because of the right angles
u wanna send the full picture
In this case I guess yes
You have 2 different areas to work on
so i need to add their lengths right? then just multiply the result by 2x-50?
ohh cmon dont leave me now it would be the second time. We got so far
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can someone help me with b
1.9?
No, that's the diameter
1/2×πr² ☠️
Ideally we'd want elpims to figure out how to calculate the area
But looks like they are gone 
ether
ya
ight so what would the first one be?
I'll give you a hint
||you know radius is 7 so we use our formula pi * r^2||
||which would be pi * 7^2
which simplifies to 49pi||
That's good
okay so
in b we see that we got the diameter and its a semi circle
@sudden sparrow you here?
yup
yea
ether
$r = 2/d$
ether
basically we got the radius of the circle now but the thing is
we have a semi circle
$\frac{\pi r^2}{2}$
ether
We can sub r into that
@sudden sparrow Has your question been resolved?
@sudden sparrow helllloo
@sudden sparrow didnt you post that exact semicircle problem before?
like, with the same diameter of 1.9m
and then our convo died somehow when you asked a weird question and got an equally weird answer from me lol
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it sure is. but some ppl either don't want to or cannot communicate clearly.
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Hello, just a quick vector question
consider those two vectors
<siunitx>
you would have [
\abs{A \cross B} = 4.6 \textsx{cm}^2
]
the cross product would be in the -z-direction by the right hand rule
so is it correct to say
[
\vb{A} \cross \vb{B} = -4.6\vc{k}
]
but it isnt is it
Isn't cross product of two-dimensional vectors a number?
Or the z axis just isn't shown here?
Yeah it is
what do you mean?
oh is it simply -4.6k?
As I remember, cross product is a vector when you have 3 or more dimensions
But in two dimensions its a number
Uhhh idk about the negative sign but if k is the unit vector orthogonal to A and B in the right direction using right hand rule then you simply scale it by the magnitude of the area between A and B
That number is called the determinant
yeah but like thats
hey derpzy 
surely not
2D can always be represented as 3D with the 3rd dimension supressed so that doesnt really matter
you can treat it as either a number or a vector with magnitude of that number in 2d
oh huh
So my calc 3 course was wrong
well
it is the determinant multiplied by the k component
if you have ai bj
you find the det between the two vectors then multiply it by k
that's what i've always done anyway 
so if i got what duh hello said, either
[
\vb{A} \cross \vb{B} = -4.6\vc{k} \
\vb{A} \cross \vb{B} = -4.6
]would be correct?
ehh, depends on what you are using it for
if you are trying to find the area these 2 span
then the 2nd with the proper units will also be right
but for the definition of the cross product i would say its not really right
the question is simply this haha
okay TIL, i never realised this
magnitude is just a number but the cross product is a vector
yeah
And anyone who says it's a number is a liar
yeah i guess the second would be more about the magnitude, but you still have that - for the direction so idk
but again it just depends on what you are using it for. the cross product can be used to find the area of the parallelogram of the 2 vectors, but that doesnt mean that the cross product is the area of this parallelogram
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👍
.reopen
✅
wait actually before that
i have a continuation question with the actual question
so now, if I were to find [
\vb B \cross \vb A
]
I know that would just be equal to $-\vb A \cross \vb B$, but how are you meant to calculate that?
like is the angle now theta = -120?
yeah basically, you are just starting from B checking how large the angle to A is, you can either go "backwards" 120, aka -120 or forwards 240 degrees
ohh i see i see okay
so like
u just start from the first vector and go to the other
wait
but wait
like
going from B to A would be counterclockwise
and this one positive
can use right hand rule to verify
yeah amazing
but wait like thats the formula for magnitude right
so how are we retrieving the direction too with the signs too
well in a right hand coordinate system the z axis would be pointing out of the paper
so the sign just tells you whether its out of the paper or into it
Using the unit vector n cap
If you look at the formula of cross product, its actually absintheta ncap
Here n cap is calculated as said by Duh hello using the right hand thumb rule
i mean it comes from the determinant definition of cross product
$$A\times B=\det{\begin{bmatrix}
\hat{i}&\hat{j}&\hat{k}\
a_1 & a_2 & a_3\
b_1 & b_2 & b_3\
\end{bmatrix}}$$
Duh Hello
the n cap or $\hat{n}$ you are talking about gets defined after the fact, its just the normal to the plane that the parallelogram that these vectors make
Duh Hello
Well that is the direction right?
yeah but the way you are phrasing it makes me think that you are using this thing that gets defined by the cross product to define the cross product
but yes you are correct, the normal vector and the sign of the cross product will tell us which direction it is pointing, but i think lix was wondering how this direction gets chosen in the first place. and its from the determinant definition which follows the right hand rule, and hence why the cross product also follows it
no but like
oh wait
hmm
okay never mind haha i got it i think
i was just confused because like
from what i know
[
\norm{\vb A \cross \vb B} = \norm{\vb A} \cdot \norm{\vb B} \map \sin \theta \
\vb A \cross \vb B = \norm{\vb A} \cdot \norm{\vb B} \map \sin \theta \cdot \vc n
]
if this makes sense?
like what i calculated was the first
Oh no i was just reminding the fact that ncap is responsible for the direction
so in my mind, the negative sign should've not came up with that, because it is just the magnitude
but rather you have to find what the direction is using the right hand rule
thats what my confusion is i guess
hmm, ok now im a bit unsure as well. i guess the first one isnt actually the magnitude
since sin can be negative
looks like we need a couple more | | s 
Vectors lie between 2nd and 1st quad only
Where sin is always positive
im talking in general

updated
thats not what i meant lix 
around sin
but if you want it like that
Well in general sin could be negative but not here i guess
[
\norm {\vb a \cross \vb b} = \norm {\vb a} \norm {\vb b} \abs {\sin \theta}
]
where the angle θ is measured according to the right hand rule
meaning it can be negative
(looking at you twerkingbee 👀)
so why this distinction then since seemingly they are identical 
they both give you the direction and magnitude
👁️👄👁️ no
Duh Hello
As far ss i remember
Our physics teacher said theta is the lesser angle
We have not done vectors in mathematics yet
But this is my memory from basic mathematics lectures
Which is required for physics and all
no idea what you mean by the "lesser angle"
depending on which way you are going, i.e with the clock or against the clock will decide which sign the angle will have, but it doesnt matter whether you choose -120 or 240, both are the same
By lesser angle i mean that if alpha and beta are the angle btw two vetors clockwise and anti clock and alpha>beta in magnitude we will take beta and disregard alpha.
excuse the horrible drawing. if we are taking the cross product between A and B we have the blue angle 120 degrees and red angle 240 degrees. what are we supposed to use here?
Blue one
I guess he said this because in physics vectors only lie between 0 to 180 not sure about mathematics tho as we are yet to study that in the next grade
oh actually i made the example wrong, ok instead we are taking the cross product $B\times A$ which angle are we using then?
Duh Hello
kinda weird that we are supposed to go with the clock with cross products instead of against it
but anyways, in the case of $B\times A$ we are supposed to use the red one
Duh Hello
now the red one is equal to the negative of the blue one
so you can of course use that one instead
but then you need to use -120
it doesnt matter which angle you use so long as you measure counterclockwise according to the right hand rule 😐
This is what i mean
no apparently you are supposed to measure it going with the clock if you think of it as going from the first arrow to the 2nd arrow
if you are thinking of it as starting on the 2nd and going to the first then yes its counterclockwise
i have no idea what you're on
going from a to b is a clockwise rotation
in an ordered basis, take a as your first basis vector, b as your second, then that defines a coordinate axes
the angle is measured counterclockwise just like in the xy plane
if you go counter clockwise you would get 360-θ
it doesnt matter which angle you take
because itll be signed measure
counterclockwise being +
uhh, in the example of θ=30 then we would have 330 which is -30 so you would get opposite sign no?
aka $B\times A$
Duh Hello
what example
I get it now lol we were not told about negative and positive angle conventions, i guess that statement of his was probably for the students not to get confused as we barely knew any trigonometry at that time
for a x b
hell, you can even go around the circle 42069 times if you want
doesnt matter
lol

ok mb, been ages since ive been working with the non determinant cross product
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Need help ehhm
Thomas ang gerry are on opposite sides of a building and are 50m apart. From thomas position, the top of the building has an angle elevation of 50 degrees. From gerrys position the top of the building has an angle of elevation of 60 degrees. How high is the building?
I have a dumb answer
50-x/√3

Sorry mate
I'm dum
welp
I mean
I think you can divide it in the ratio of 3:2 by seeing the diagram
But what i see isn't always true
So idk
If that turns out to be true then the answer could be 20√3/3
Have u tried sine law?
actually i would just use tan(50°) and tan(60°)
let the height be h, and then use tan(50°), tan(60°), h and 50 to make a equation
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Someone readyy
seee
The figure below shows a cross section through a pool triangle, which has the shape of an equilateral triangle and is drawn in red.
Each ball has a diameter of 57mm.
(a) Argue that angle v is 30°
(b) Determine the distance |P S|
(c) Determine the perimeter of the red triangle
@tardy burrow Has your question been resolved?
help...
hi
is QSP a right angle?
yea, i think if we can prove QSP is a right angle, then we can find v is 30°
@tardy burrow Has your question been resolved?
yea
I think soo
what we do know
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why take the limit and not just plug it in
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im not sure how to solve this
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I need help
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Can someone help me understand how to evaluate this?
looks like a substitution is in order
This was my answer. I double checked with calculator and it says I'm right though..not sure if im putting it in wrong
It's just telling me syntax error..
probably because of the powers on the cosine but
I think you might have forgotten to actually increase the powers
you integrated u^3/2 - u^7/2, right
ah no
ok it's good
from u^5/2 to 2/7u^7/2
Just try writing cos(x)^(3/2) instead
and radical u to 2/3u^3/2
ok
maybe the 3/2 and 7/2 should go in front of x?
what does it look like reformatted now?
Okay I understand..my powers were in front of (x) which is illegal..
yeah sometimes it's fine
idk if it doesn't like it with fractions or what
maybe they just never happened to build it in
would make it harder to detect correct answers
(though not really much)
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Hello
cross multiply then simplify
no dont expand the bracket
cross multiply with the bracket
to remove the fraction
yes
what now?
now how do u get k to be by itself
taking out the xy and (z+w)?
yes
so divide both sides by that
like the whole left part by xy?
divide both sides by xy(z+w)
HOLY FUCK I MASTERED MATH
so with equations like this it's always the same procedure?
p much
hold on a second there's something weird
try do a diff question like that
number 2
yea it should be - not x
yes
np
u need to find x?
it asks what's the smallest value of x
can you use your calculator?
nope
oh damn
this is a < one minute quiz during the exam that includes three math seasons that include one which consists of 20 quizes with a timer of 20 mins before flipping the page
hmm how so
x^2 - 7x + 10 = 0
yes
now put it into brackets
i see what you did there
x^2 - 7x + 10
u put that into brackets
if you expand (x-5)(x-2)
you get x^2 - 7x + 10
so (x^2)-(7x+10)?
i can learn
you need to basically put it into a format like (x- ) (x- )
think of 2 numbers that add to -7 and multiply to +10
yeah
anyone there



