#help-39
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I dont know how to set up the matrix
make a matrix and edit it to the coornets
?
edit the values till you find what you need?
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How can this be simplified? Not used (a+b)³ formula
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I've figured out that AB has to be 8, so does B
And BC is 6
and CD is also 10
So I have enough information to determine the area of both circles
But I don't know what they mean by the area between the two circles
<@&286206848099549185>
ok
so then its
64?
*64pi
?
<@&286206848099549185>
Cans you please confirm the answer
?
@midnight haven Has your question been resolved?
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This ain’t right
yes
Iiii gotcha!
@rain flame Has your question been resolved?
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I don’t know where to go from here
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81 27 9 3
explicit sequence
neat
hey
do you have a question about that sequence?
the 0th tterm is 81
so the 1st term is 27
ok
so what can the explict seuqnce be? 81*1/3^n-1?
but that owuldnt make sense
these are all powers of 3 yes?
yea, the previous term is multiplyed by 1/3
ok so you could make a formula that looks like 3 to the something power
where "something" is a formula involving n
so 81*1/3^n?
,calc 81*1/3^0
Result:
81
,calc 81*1/3^1
Result:
27
yep that'll work
i got it
@west sapphire wait
i have a question tho
is n equal then or grater then 0?
well you plugged in n=0 and n=1 and got the right answers
so n equal then or greater then 1 or 0?
assuming your sequence index is starting at n=0
so its 1
i don't know, you tell me
it cant be 0
why not
people define sequences starting at n=0 all the time
but it's your sequence, you tell me what the first n value is
but only if the 1st term is considered the 0th term?
it's not up to me to decide
the 0th term is 81
if we call your sequence x(n)
mhm
does it start like x(0), x(1), x(2),...
yer
not in my case
because the problem spefically says that the guy makes cuts
if i make 0 cuts on my paper
im left with original size
which is 81
well you haven't pasted the problem statement
sorry, but u understand right?
what if it was 81 27 9 3
81 was first term
it would be n equal then or grater then 2
and 81*1/3^n-1
why
,calc 81*1/3^1
Result:
27
yup
i think im correct
@west sapphire am i
@west sapphire
@west sapphire bro
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The question says to find k so that the equation is a perfect square trinomial but how is it 12??
Does the 9x^2 have anything to do with it?
b^2 - 4ac = 0
Do I just remove 9 by divide
Or do I have to multiply 9 by 12 as well
that is not correct
a, b, and c are the coefficients of the x terms
so we dont take the x term with them when we say what a, b, and c are
so it would just be
a = 9
b = -k
c = 4
Oh
b^2 - 4ac is the determinant
it determines how many roots a quadratic has
since your questions asks for a perfect trinomial
that means it has only 1 root
so b^2 - 4ac = 0
I don’t think I learned about determinants in my class yet
oh
alright
another way to do this question then
is to look at the x^2 term and the constant term
which have been given
9x^2 = (3x)^2
correct?
and 4 = (2)^2
I don’t see 3x or 2 in the equation
well no but im just simplifying the terms
if we want $9x^2 - kx + 4$ to be a perfect square, then it has to be of the form $(ax+b)^2$
nalin
Yes
and $(ax + b)^2 = a^2x^2 + 2abx + b^2$
nalin
Ok now you lost me 
i just expanded (ax+b)^2
Ok
understand what's going on?
im coming to that
you dont have to get rid of it
so $a^2x^2 + 2abx + b^2 = 9x^2 - kx + 4$
nalin
do you understand this ^
Yea
ok so now we just have to compare the coefficients
$a^2 = 9$; $2ab = -k$; $b^2 = 4$
nalin
alright?
It’s weird because their were 2 other problems very similar to this right before and they were easy because a=1
Yes
nalin
okay?
I got the answer already but again I’m not sure if we learned the 2ab part in class 😅
which 2ab?
You plugged in 2ab to get 12
oh
yeah
i think you would've learnt it but you must have learnt it only for a = 1 so you would've seen it as 2b instead of 2ab
but idk how else you're supposed to find k than to find 2ab
Next time I’m at math I will ask if there was a specific way to do it because I don’t remember doing these kind of questions tbh
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@rocky bluff Has your question been resolved?
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this question is stressing me out i dont know how to partition a segment or do this at all
Can you figure out the length of pq?
@gloomy aurora Has your question been resolved?
what confuses me is how to apply the midpoint formula to my question but more specifically the steps
wdym?
i understand the concept but i dont know what to do to find R
add both x1 x2 and y1 y2 then divide both of them by 2 to find the coordinates
ive done that with PQ but im not sure if im right
show what you've done
yeh, its correct
okay but as for RQ i dont understand what to do…
i think my issue is im not understanding it the way i should
@gloomy aurora Has your question been resolved?
oh really??
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dont i have to use the ratio for something though
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Yo
How would i solve this?
is there a actual process or do i just keep guessing numbers?
Are both 'F's the same?
yeah
So sub this into the the line above
Kai Funaba
Notice anything similar?
the F(T)
0
Now sub 0 into the first line
sub it for what tho in the firts line?
Which is "f(T)" ?
So you can solve it with factorising or quadratic equation
Step by step
They can't see y they need to sub 0
Oh ok
So 0=T^2-9T+18?
Yep
gotcha
$$T^{2} - 9T + 18 = 0$$
Kai Funaba
so i slide it over?
oh okay
I just prefer it on the right
I see
Then just factorise the rest
You can substitute back to the equation to verify the answer if it's equal to 0, but yes, that's correct
So id write T=6,3?
T = 6 or T = 3
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. close
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Cos(x+π/3) is = sin(π/6-x) right?
@ornate tundra Has your question been resolved?
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you will have to explain what this notation means.
divides?
otherwise it is impossible to give hints.
@opal forge Has your question been resolved?
I don't know what they meant
then neither do we.
I thought maybe it is a famous notation and you guys know
Answer is given B
Let me show you the solution
654
formally this does not give us enough info to decipher
but MAYBE (big maybe) this fraction-looking slash symbol means "divides"
which i personally have seen written with a vertical bar
in which case yeah this is about remembering properties of divisibility
no tips can be given you just need to know this
it is almost like vocabulary knowledge
yes the solution is correct
I am taking random numbers for checking this
I checked by taking random numbers
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need help on this
to remove the log on the left side, raise x to the power of a on the right side. then to isolate x, raise the power of the a on the left side to 1/a
you mean multiply by 1/a?
no
oh wait i got what you mean
$log_{x}{a}=a\implies x^{log_{x}{a}}=x^{a}$
calculus is fun
oh i get it
from here you get $a=x^a\implies a^{\frac{1}{a}}=(x^a)^{\frac{1}{a}}\implies a^{\frac{1}{a}}=x$
calculus is fun
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for this
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At a catering establishment, Crissie bought some trays of food for $31 each and some side dish for $9 each. If she spent a total of $305, how much did she spend on side dishes
Is there a quick way to do this?
Like to restrict solutions to whole numbers instead of guesswork or diophantine (for integers)
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@oblique reef Has your question been resolved?
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some basic trigonometry help, what's CB length ?
it's supposed to be a right triangle ye
You can use the geometric mean theorem
and the P is the force applied which will make a little more angle
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what is the thought process of doing this
this is a multiple choice question so I can't spend more than like 2 minutes on it
that is if I were in an actual test but I'm not
Concave up happens when $f''(x)>0$
PajamaMamaLlama
but its the graph of f(x) so wouldn't that change things around?
the graph of f is concave up when:
yes this, bad wording on my part 
because I only know using the 2nd deriviative to find the nature of the first derivative
or inflection points
so I don't really know how f(x) and f"(x) relates
f'(x) is the gradients, f''(x) is the 'gradient of the gradient function' i guess
when f''(x)>0, f'(x) is increasing, so f is concave up
and hence f(x) is concave up as a result
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for number 11
how do they find the length of the integral from t=0 to t=2?
how do the point corresponds to the t values?
heres the full solution
is it because we are dealing with trig function so it has to start at 0 and end with 2 pi as a full rotation?
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@fickle finch Has your question been resolved?
@fickle finch Has your question been resolved?
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where does the 3/2 in the power come from
,tex .exp rules
hayley.bin
which rule?
well, you'll need a few
perhaps you might start with the one that has the radical symbol in it
can you elaborate further
@still patrol Has your question been resolved?
<@&286206848099549185>
Percy
Yes
what is the power of t in the numerator?
1
t^2 * p2 * p3
yeah
Yeah and😂
Percy
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yeah yay
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help
with?
💀
😭
💀

i think he needs help
not enough twinks 
seems like we got epicly trolled
P (2x-1) = x^2 - 3x + m + 1
and
the sum of the coefficients for P(x+6) is 2
then what is the constant of P(x+3)
i dont get the logic behind this at all
my teacher basically solved it like
ok to find the sum of the coefficient u give x 1
so p(7) equals 2 then
but
the thing i dont get is
ok if someone can vc about this thatd be great too but like
if no one can i’Ll jus type
we usually type here
i wonder if we have vcs here
we dont
yeah
hm
yes
my brain is asoup
not enough twinks 💀
and for constant, you do ||P(0)||
then by logic, shouldnt we
yeah
instead of saying p(7) equals 2
no we shouldn't
x+6= 1
life's tough
then x is -5
then so we put that x value in the polynomial given abve
or some hsit
no it isn't 💀

so p(1+6)=2
x+6 isnt the variable? x is?
see thats wrong
is anyone able to help me with this?
i'm confused about this whole question 😭
bruh
same 💀
<@&286206848099549185>
apologies lmao
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asked to turn this into standard form
is it a polynomial?
yep
unknown degree?
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if i have matricies a and b, is (-a)*(-b)=ab? if so, why?
yeah. its because -a = (-1)a, and the scalars commute with matrix products
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How do I prove that there is no more functions left in functional equations?
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A =
[−12 6
14 −7]
Hello I'm trying to find what B would have to be to get AB = 0
how could i achieve that?
wdym solve for Ax = b?
The strategy is to find each column of b independently
A single column can be though of as a vector
im sorry but im unaware of how to do that
You mean solving Ax=b?
yah
Have you not done anything like gaussian elimination?
maybe? idk the name of all the things they want me to do
Alright I think I got a simpler way
you can also notice that -12 = -2*6
and 14 = -2*(-7)
so if you take
B = [1
2]
it will give you 0, and any column of B has to be of this form
the 2nd line of B has to be twice the first line
Lmao same
I was gonna say use definition of matrix multiplication
Haruno -> if you're familiar with linear algebra, B has, as columns, vectors of the kernel of A since AB = 0
but the kernel of A is obv of dim 1 and we guessed (1, 2) was in it, so it's span{(1, 2)}
so 2nd line of B has to be twice 1st line
Oh I see
That sounds a bit advanced to understand though if they havent learned how to solve Ax=b
yeah but if he can see how it has to be true for each column individually, which you explained, then there's no need to talk about the advanced stuff
I see
once he does it for one column of B, each column is the same calculation
im not sure what calculation u mean
you take a matrix
B = [a1 b1 ...
a2 b2 ...]
and you calc the product AB
and you equate it to 0
you'll see that the only condition is a2 = 2a1, b2 = 2b1 etc
you'll conclude that AB = 0 iff the 2nd line of B is twice the first line
because it's the same calculation for each column of B again and again
it always only gives the condition 2nd line = twice 1st
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Hi, how would I do this?
finding g(3) is trivial
for g'(3) (slope at x=3) slope is same as slope of tangnet line
Oh
Idk what integrate means and idk the equation
Alr
Yep
I get that
g(3) = 3
Sorry I'm still unsure
So g(3) = 3
Obviously
What about g'(3)
as I said the slope of a function is same as the slope of the tangent line
so you need to find the slope of tangnet line at x=3
the question gave you two points on the line so you can calculate its slope
you have (3,3), and (1,5). find its slope
-1
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if f(n) = 1/n^2 and g(n) = n what is f = ?(g), answer can be big O or theta and the smaller counterparts
Please don't occupy multiple help channels.
this should be O right because when n approaches infinity it gets smaller
or am i missing something
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can someone pls help me with this
pls pls pls
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Would someone explain to me what happened between 1:07 and 1:21 on https://youtu.be/765X_PAxhAw ? Transcript on https://www.khanacademy.org/transcript/x03a2d28c
Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now: https://www.khanacademy.org/math/differential-calculus/dc-chain/dc-implicit-diff-advanced/v/derivative-natural-logarithm
Differential calculus on Khan Academy: Limit introduction, squeeze theorem, and epsilon-delta definition of limits.
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how do you differentiate $e^{y(x)}$
Denascite
I'm not sure does the (x) next to the y mean.
does it mean you input x and it gives you y?
I know the power rule for the former and from repetition know the 2nd.
do you know the chain rule
I've seen it but know know in which circumstant to apply it.
you use the chain rule whenever you have a composition of functions
e^sinx is a composition of the functions f(x)=e^x and g(x)=sinx.
e^sinx = f(g(x))
oh nice
so e^y*dy/dx mean "we're interested in derivating y in e^y" ?
if not, can you phrase it in common language?
its an application of chain rule
outer derivative times inner derivative
f'(g(x))*g'(x)
if you have seen that before
for us f(x)=e^x and g(x)=y(x)
so we get f'(y(x))*y'(x)
f'(x) is still e^x
so f'(y(x))=e^y
and y'(x) is the same as dy/dx
y'(x)=1 right?
in general no
y'(x)=1 for this case though?
no
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@undone oasis Has your question been resolved?
In the video, this is what they are trying to find y'(x).
They start with y = lnx, then change it to exponential form
e^y = x
Take derivative with respect to x on both sides:
d(e^y)/dx = d(x)/dx
d(e^y)/dx = 1
As Denascite explained, for the left side you need the chain rule because y is a function of x: y(x)
Then they solve for y'(x), use the fact that e^y = x, and you get
d/dx (ln x) = 1/x
because y is a function of x: y(x)
does that mean the function y=1x+0 ?
no, y(x) = ln(x)
a(b) is a way to say that a is a function of b
same as a is a function with variable b
so
for us f(x)=e^x and g(x)=y(x)
should have been
for us f(x)=e^x and g(x)=y(x)=ln(x)
?
Yes g(x)=y(x)=ln(x) is a correct equation, but setting g(x)=ln(x) would be useless in this case because we're trying to find y'(x)
so just say g(x)=y(x)
otherwise, y(x) "disappears" and we won't get any info about y(x)
could you expand?
let's say you use this
for us f(x)=e^x and g(x)=y(x)=ln(x)
then f(g(x)) = e^(lnx) = x
The function y is gone as it was simplified, and we can't get it's derivative
Mmm still that's kind of arbitrary, you can do it in any way you like as long as you know what you're doing 🤔
Did you follow the procedure until this part?
d(e^y)/dx = 1
I stopped at the line right above the 1st dy
They start with y = lnx, then change it to exponential form
e^y = x
Do you get this?
I understand it as you give ln x and it gives the result of e^x, and results are y
mmm ok
y = lnx <-> e^y = x
these are equivalent
yes
ok
Now we use this: e^y = x
Take the derivative with respect to x of both sides
$\frac{d}{dx}\left(e^y\right) = \frac{d}{dx} x$
ELeonardo
please @ me when you get back to this
I was expecting questions haha, ok
d/dx of x is just 1
$\frac{d}{dx}\left(e^y\right) = 1$
ELeonardo
e^y is a composition of functions:
f(x) = e^x and g(x) = y
When they are composed:
f(g(x)) = e^g(x) = e^y
The chain rule works for compositions
Chain rule:
$\frac{d}{dx} f(g(x)) = f'(g(x)), g'(x)$
ELeonardo
g(x) = ln(x) = y right?
yes
we're working with e^y, not e^lnx
of course in this case they're the same because y=lnx
but we're using y for now
using y while not including ln(x) seems obvious to you but not me, I have to keep seeing it.
I mean is just a way to write it
And it's better for now, so you can learn
after you learn this totally, you can write it as you like
Remember that we want to find the derivative of ln(x)
In order to do that, we start from
y = ln x
whenever you see y, it's lnx
ok, but at the end I'll just copy-paste all y's by ln(x)
ok ok I think I get your point. Sure we can use lnx as long as you don't simplify it
in that case, we have
$\frac{d}{dx}\left(e^{\ln x} \right) = 1$
ELeonardo
cool
Terms we need for chain rule:
f(x) = e^x and g(x) = lnx
f'(x) = e^x and g'(x) = (lnx)'
f'( g(x) ) = e^lnx
$e^{\ln x} \left(\ln x \right)' = 1$
ELeonardo
ok so far?
yes
ok now, (lnx)' is another way of writing d (lnx) / dx
$\frac{d}{dx}\ln x = \frac{1}{e^{\ln x}}$
ELeonardo
I'm not sure if I'd get a mistake if submitting it to a teacher, but for me it's A ok.
ELeonardo
.close 300
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the answer is 2 + root 5 but how do i get to there
x = 2 + root 5 btw
uncrop
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uh no
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can someone pls help me with this?
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x^2 + y^2 = 82
-x^2 + 2y = -19
Can i get some help solving the system of linear equations
i have absolutely no idea what to do with it
a good first step would be to add the two together
Elimination should be easier here
you can do it either way. sometimes its easier to do one way over the other.
so y should be
y = -9
y = 7 ?
almost
oh? what did i miss
no nvm you got it
looks right to me
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remember though its +- 1 and +- sqrt(33). since it was a square root.
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oh lord
idk if i'll ever rememebr that
do i put +- in the solution or
just put 4 solutions
prob in the solution that i look at it
it's technically 4 solutions, since you are finding where both equations are equal (where they intersect)
and they intersect at 4 points
do u know if using a graphing calcualtor (ti-84 plus cs) is there a way to accurately view the points they intersect at
or is that a lost cause
you could, i think. let me see
ugh
yah but do u know if theres a way to view the points accurately?
where they intersect
i feel like there should be or graphing this stuff on a calculator would be pointless but idk
which button is that?
[2nd][Trace]
you have to pick two curves, then look for a point close to the intersection
and it'll find it
you trace with <- -> and you pick curves with ^ and v
when graphing these curves though, since they are relations you have to solve for y to put it into the calculator to graph
thats why i had to use two curves to fully graph the circle
ahh alright
graph looks better with ZoomSquare
is that a calculator thing or?
np
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In one model, the biceps muscle of a particular person can be described by the body of revolution that appears when the graph of f is rotated 360° around the prime axis in the interval [0;40].
f(x)=2sin(0,05πx-0,5π)+2
Strength of the biceps muscle is proportional to the maximum cross-sectional area of the muscle. Determine the maximum cross-sectional area of the biceps muscle
@left crane Has your question been resolved?
nope
@left crane Has your question been resolved?
nope
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An arch has the shape of semi-ellipse that is 10 ft. long and 3 ft. high at the center. How high is the arch at a point 3 ft from one endpoint of the base of the arch?
Anyone have any ideas about this?
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hi guys I need help on how to find side lengths of a triangle if I only have angles and the triangle isn't a right triangle so I can't use sohcahtoa
I'm supposed to use sine law and cosine law but I'm not sure which one to use since both of them use side lengths
I don’t think it’s possible if you only have angles. No side lengths at all?
There are infinite amount of solutions
@gaunt ocean Has your question been resolved?
wait nvm there is 1
can I show you the question?
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help
can someone explain how to prove k ≠ 0
its not listed as an answer bu
is it part of the answer?
this is a graph, and y = 0 only intercepts once
cuz C = 0 only has one solution
and when you sub k = 0 into the equation
this one
you only get one solution, x = 4
but when you solve discriminant > 0 you get k = 0 within the range
discriminant = 1 when k = 0
is it because the equation becomes linear, so discriminant doesnt aplly when k = 0?
<@&286206848099549185>
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this may or maybe not be one of the reasons, but I didn't prove or disprove it so i can't tell.
But this is the case causing trouble in some of the "original" quadratic equations.
But another thing is that, when you have kx²+.....=0
you need to divided by k to get the roots, but the point is k cannot be zero in order to be divided, hope this helps!
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@opal forge Has your question been resolved?
the minimum of what?
@opal forge Has your question been resolved?
can you explain this
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I only assumed for it
z is complex? and |z| = a^2 + b^2 then? (if z = a+bi)
try plugging in each number and see if the number you get ends up being less than or equal to 6
you can find the answer that way
or, you can combine the two absolutes
|z + 2| + |z - 2| is the same as |z + 2 + z - 2| or |2z|
so you can also check |2z| <= 6
that's so false lmao
is || abs value for integer or complex?
like is z integeral or complex
both cases lead to spoutshield saying something false, even in the complex you don't have |z+2| + |z-2| = |z+2+z-2| (the triangular inequality implies <=, with them being different for most numbers, like 2i)
|| is comprehensible as a distance, z being complex or real
i was confused for the complex case, thanks for confirming my suspicion
okay, thx!
Of course complex
Wow
well have u tried substituting? it would be painful but shouldnt be too bad
$\sqrt{(a+2)^2 + b^2} + \sqrt{(a-2)^2 + b^2} \leq 6$ \\
Since square root cant be negative, \\
$0 \leq \sqrt{(a+2)^2 + b^2} + \sqrt{(a-2)^2 + b^2} \leq 6$ \\
ItzKraken
$(a+2)^2 + b^2 + (a-2)^2 + b^2 + 2\sqrt{((a+2)^2 + b^2)((a-2)^2 + b^2)} \leq 36$
ItzKraken
$2a^2 + 8 + 2b^2 + 2\sqrt{b^4 + ((a+2)(a-2)b)^2 + ((a+2)(a-2))^2} \leq 36$
ItzKraken
$2\sqrt{b^4 + ((a+2)(a-2)b)^2 + ((a+2)(a-2))^2} \leq 28 - 2(a^2 + b^2)$
ItzKraken
$\sqrt{b^4 + ((a+2)(a-2)b)^2 + ((a+2)(a-2))^2} \leq 14 - (a^2 + b^2)$
isnt that with absolute value?
and equality only and only if a=b?
$b^4 + ((a+2)(a-2)b)^2 + ((a+2)(a-2))^2 \leq 196 + a^4 + b^4 - 28a^2 - 28b^2 + 2a^2b^2$
ItzKraken
$b^4 + (a^2b - 4b)^2 + ((a+2)(a-2))^2 \leq 196 + a^4 + b^4 - 28a^2 - 28b^2 + 2a^2b^2$
triangle inequality solves it directly
huh..i never applied the inequality outside of geometry
i never applied triangle inequality in my life
,w simplify b^4 + (a^2b - 4b)^2 + ((a+2)(a-2))^2 \leq 196 + a^4 + b^4 - 28a^2 - 28b^2 + 2a^2b^2
how do u know it works then 
i just applied it when helping others sometimes when needed
but i never had to use it
oh i see
hey arjunn
use triangle inequality it gives the answer faster
$|a+b| \leq |a|+|b|$
calculus is fun
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Ok I have epic solution -
|Z-2| is distance of z from point (2,0)
|Z+2| is distance of z from point (-2,0)
Now what is the locus of a variable point whose distance from 2 fixed points is constant
It's an ellipse
So you have an ellipse with foci (±2,0) and major axis 6
|z| is distance from origin which is the centre of ellips
So max distance from centre will be semi major axis =3
@opal forge
Yes I'm reading
what are a and b here
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How do solve this
Wdym
squaring both side?
