#help-36
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for finding easy primitive
so it would work here
i could say u = ln(x)
go bolder
1/(x ln(u)) after the u-sub
1/uln(u)
i said u = ln(x)
yes
du = 1/x (dx)
yep
so we have 1/ln(u) du?
where du = 1/x dx and u = ln(x)
?
that would have been for...
$$
\int \frac{1}{x \ln (\ln (x))} d x
$$
Substitute $u=\ln (x) \longrightarrow d u=\frac{1}{x} d x$:
$$
=\int \frac{1}{\ln (u)} d u
$$
dgh
this integral
We have 1/(xln(x)ln(ln(x)))
unfortunately the reason I told you to multiply by 1/ln(x) is because 1/ln(u) is indeterminate (at least no simple primitive
i've not understood the reason we would do 1/ln(x) multiplication yet
you know what let's stick from here
do we agree that ln(u) < u?
so 1/ln(u) > 1/u
okay
so this integral $\int \frac{1}{\ln (u)} d u$ is bigger than...
rafilou2003
int(1/u)
ln(u)
and what can we say about ln(u) when u gets to infinity?
it goes to infinity
uh huh
and so this integral?
goes to infinity?
diverges
or i mean, depends on the endpoints, it's not 0 atleast
so this sum?
one of the end points is 30
diverges?
the other is infinity
by integral comparison test
the integral comparison test part was?
$\sum f(n)$ has same convergence type as $\int f(x)dx$ when $f$ is decreasing
rafilou2003
(and integrable)
okay and f is decreasing because the denumerator is increasing -> inverse is decreasing?
yes
the part that confuses me is we're talking about sums in the first part
adding something means we add something so it becomes bigger
but how is it similar to an integral which kind of calculates infinitely small rectangular areas?
the proof is here if you want to check
an integral is an infinitesimal sum of those rectangles
okay so to summarize how the problem was solved
\begin{enumerate}
\item Ensure the function (f(x) = \frac{1}{x \ln(\ln(x))}) is continuous, positive, and decreasing for all (x \geq 30). These conditions are necessary for the integral test to be applicable.
\item Use the integral test, comparing the series to the integral of its continuous counterpart. Thus, we set up the integral (\int_{30}^{\infty} \frac{1}{x \ln(\ln(x))} , dx).
\item The integral (\int_{30}^{\infty} \frac{1}{x \ln(\ln(x))} , dx) was calculated. The result of this integral indicates the behavior of the series.
\item If the integral is finite (converges), then the series also converges. If the integral is infinite (diverges), then the series diverges.
\end{enumerate}
dgh
that's it
or technically we didn't do step 3
@rustic trench Has your question been resolved?
@scarlet sequoia got time for this?
also i have a follow-up question if you got time
ping me when you see this
@rustic trench Has your question been resolved?
we didn't do step 3 because we computed something smaller that went to infinity
we've shown that $\int_{30}^{\infty} \frac{1}{x \ln(\ln(x))} , dx \geq \infty$
rafilou2003
rafilou2003
how is something geq infinity, infinity doesn't ever end? actually i don't recall how we've shown that function goes to infinity, isn't the function technically just decreasing?
and i don't recall this part, when did we change the endpoint with ln(30)?
well if it's equal to infinity
the function integrates to ln(u)
u sub
the bounds change
and when you get $[\ln(u)]^{u\to \infty}{u=\ln(30)} = \lim{u\to \infty}\ln(u) - \ln(\ln 30)$
rafilou2003
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Hello I need help solving this problem
so I’ve started by trying to use induction on n
the induction step is really simple
What’s hard is proving the base case
I know I can argue that if o(t(0))=o(o(0)) then by the peano axioms that implies t(0)=o(0)
I’ve also thought about left inverses since I know t and o are injective by peano axioms
however I still can’t seem to get anywhere with this proof
Also sigma ( or o ) here represents the usual successor function
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for the inequality 2cosx(cosx - 1) > 0, the only thing we need from the (cosx - 1) part is it's critical value because cosx > 1 is never true right?
it's never true, so if the inequality holds, that means you have 2cos(x) times a negative number is positive
which tells you what about 2cos(x)?
oh thats a very nice way of explaining this situation
it has to be negative
yep!
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How does $-1<cos(u)<1$ imply $cos(1)<cos(cos(u))<1$?
Why am. I here
ur welcome
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need to determine the derivative
I used product rule here because it made sense
but I dont' seem to be on track
$(\tfrac12 x ^{-\tfrac12})(x^3-x)+(3x^2-1)(x^{\tfrac12})$
wyldinwilliam
so far ok
@tranquil pine Has your question been resolved?
<@&286206848099549185>
it looks very well
why is it written like this instead
your right but
I'm just curious why this format is more simplified
$\frac{\sqrt{x}(7x^2-3)}{2}$
than this ^^
wyldinwilliam
i offeerd you form as your teachers wants, since i am too. both are equivallent
it looks just nicer
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Click on MATH HELP (OCCUPIED)
o
You probably have the help channels hidden - make sure that it's expanded so you can see read ones
oh i see
but anyways
i dont get this
like f(x) isnt vertex form so what kind of form is it
like is it just partial factoring thing
yeah pretty much
um
factor first 2 terms ignoring last term
ax^2 - axs + t
yeah that is in the form ax^2+bx+c, so just do that in reverse
starting from ax^2+bx+c
ok so theres 4 forms
standard form, vertex, factor, and partially factored?
because im confused on the difference of factored form and partially factored
This isnt a commonly used form, but you could say that
fully factored is like a(x-b)(x-c) while partially would be what is shown above
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he plugged in y (prolly given in the beginning?)
oh right
lmaoo
what about this
derivative of f(x)
what rule is happening here
properties of ln
😭
uhhh
i would just say use ln properies, its more convenient cuz that approach may take longer to simplify
well more messy i should say
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Stuck on how to apply the order limit theorem to get to the last line from the previous. There doesn’t seem to be a good way to compare the two series so I’m thinking I have to apply part (iii).
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@half pumice Has your question been resolved?
maybe this is naive, but can’t you construct a sequence c_n where c_i=c for all i. then clearly it converges to c, and since c_n = c \leq b_n for all n then we can apply (ii)
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could someone help me with this question for part b?
@mellow jacinth Has your question been resolved?
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i havent learnt that yet
Oh. Then you have to do it the hard way
i know the sum and product rule
okok
Sorry
its aight dw
let r =ratio of the GS
use abc=8
show that ar=2
ay thank you
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complete the square for y
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The angle of depression from the top of the mountain to the horizon is 2 degrees. The angle of elevation from viewpoint number 1 and viewpoint number 2 to the top of the mountain is 10 degrees and 20 degrees respectively, and the distance between the two viewpoints is 12 km. What is the height of the mountain and the true radius of the Earth? There is another mountain roughly with the same height 5000 km away on the ground. Give the arc distance between these two mountains and give the straight-line distance between these two mountains.
ive found the mountain height, 4.1km
but i dont quite understand how to find the radius
@golden ledge Has your question been resolved?
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can u like draw so i can understand
hm i dont think so
from what i understand, theres a person looking from a mountain 4.1km high and hes looking down 2 degrees and he can see the horizon?
ill try draw it
alright, thanks
ive run the question through ai, and it from what ive seen its not possible to calculate the radius. I think I should just ask my teacher about this question tommorow.
maybe the question is wrong who knows
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Please inform me if there is anything that seems obscure.
I’m trying to find the t.
Then I found that angle(ADB) is 90 degrees
Which contradicts to the circumstance that lineDA and lineAC intersect with one another.
Any idea?
Is there anything wrong?
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hello
if $f$ is not piecewise continuous over $I\implies \int_I f$ diverge
Adam Chebil
can you give a counter-example to this ? (other than the popcorn function)
why not that one
it's so complicated, i couldn't even tell if it's piecewise continuous or not
well its not
thats the point
any function which is not piecewise continuous will be complicated like that
the popcorn function is a relatively simple counterexample all things considered
i mean you could define a function with only one "pop"
well that would be piecewise cont
wait, piecewise continuous according to the french definition of piecewise continuous right ?
i think i showed it to u
bla bla can be split into intervals on which it is continuous
on which it is piecewise continuous
no on the individual intervals it is continuous
ln(x) for example is piecewise continuous on ]0, infty[
would $f(x) = \begin{cases} 1 & x = 0 \ 0 & \text{otherwise} \end{cases}$ be piecewise continuous?
hayley!
its also just continuous
piecewise continuous is like the word basically says, it can be split into pieces and on each of these pieces it is continuous
every continuous function is continuous because you can split it into one piece
I think under any reasonable def it should be
this is not piecewise continuous
you shouldnt care about the jumps
you should
no otherwise floor(x) for example also isnt piecewise cont
if you want that it is continuous at the jumps then you just have a normal continuous function
can you understand french ?
no
non pas
there's no way you can split it into intervals that are continuous bc it's not continuous at 0
(-infty, 0) and (0, infty)
i think this is piecewise continuous
and who cares about jumps
the limits must be finite (not necessarly equal)
you're just leaving 0 out in the dust?
I would treat it as a "partition" and then say it needs to be cont on each open interval
which iirc is what adams book does
(for bounded domains)
yeah according to the definition, f is piecewise continuous iff f is continous on any open interval included in I
oh
the whole intuitive point behind piecewise cont functions is that they are basically continuous with maybe some jump points in between
and the limits at the bounds of every interval must be finite
@desert mantle so according to that definition, the popcorn function is not piecewise continuous and the integral converges ?
oh i meant not piecewise continous srry
yes
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how was this simplified
Consider the denominator first 2^2 = 4 and 3*4 = 12, next up with the numerator, club the like terms (4-h)^2 multiplied by (4-h) is (4-h)^3 ... Pi remains as it is.
@pine ridge You can close the question if you're done, ig
.close
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How to prove triangle △MNE is similiar to △ECD
I suppose MN and CD are parallel as well?
Only then, you can argue some other angles as equal as well ... Do you see how?
Segment MN is the midline of triangle ABC. Line MD intersects the continuation of side AC at point D, and side BC at point E (see figure).
1.What fraction of the area of triangle ABC is the area of quadrilateral AMNC?
2.Prove that Triangle MNE ~ triangle DCE.
full question
i have solved the 1.
I guess
Yeah, it is a theorem, the midline MN is parallel to the base AC
and hence it is parallel to the continuation as well
Well, if MN and CD are parallel, angle MNC is equal to angle NCD, no?
bruh
ofc
how i dont see that
do you know how those angles are called?
so i can do more research on that
I dont really know all the rules, most of the time i guess by the eye
It's just parallel lines cut by a transversal, ig ... which makes a buncha angles equal
Sorry, I have been outta school for quite a long time, I don't remember the exact terminology
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No, don't do this
😄
I suggest, go read up on both the above facts I mentioned
first how the midline is parallel to the base
second, how are angles in parallel lines equal
Get an intuition as to why this is correct, and remember them for a lifetime ... Hope that helps
Yes it will thx
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triangle bisector which goes through 9cm and 6cm sides splits third side with 2 sections and one of the sections is same size as one of the side. Find third side of the triangle
I think this question can have couple of answers but in the answers page it only had 1 answer which was 10 so how can I solve it so I will have only 1 answer?
@long kraken Has your question been resolved?
well what method would you take then
like do you have a plan on how to solve it
I started with the bisector rule a/b = a1/b1 => 9/6 = (I took 9 as the section) so 9/6 = 9 /x
and then solve for x
and 9 + x = third side
9x = 54
x = 54/9
x = 6
but 6 and 9 is 15 as the third side but answer was 10
but just wait
now what are the sides of the triangle
9 and 6
9, 6, and 15
yeah
9 and 6 mnust be more then 15 right? dd
I think it could be equal to 15 too no?
so the strategy would be to check all the possible ways and then the one that is the triangle would be the answer?
well what do you mean by using 9 as the section here
bisector splits third side as 2 sections and one section is equal to one of the sides
maybe, but we'll check your method and if it works, then we'll work from that
ah
so I chose 9 as one of the section
yeah
so that's why I am confused that there is only 1 answer
so another possible equation is 9/6 = x/9
in the answers page
yep exactly
yeah but maybe some cases don't work
yeah that must be the reason
or maybe I don't give correct condition of that question
hmm we'll see if this works then
it's on Georgian language so I am not sure if it's correct
alright
so if it can't be triangle
then 2 of the equations are gone
2 of them led to 15
so either 9 in denominator or 6 in numerator
for 9 in denominator we get x = 81/6
which is 13.5
so the third side is
in that case c is 22.5
yep
but answer was 10
but again
😄
it fails
that's so confusing
wait why? biggest side is oh yeaah
big side should be smaller
then other 2
yeah
ohh that must be the solution elimination of other cases
4
yes
but there is one issue
so the third side is 6 + 4
I found out just now
here is the problem
we can't assume that 15 is not the answer
it could be equal
to third side
yeah
yeah but confusing part is that answer was only 10
in the answer's page
so that's so strange
idk does the question talk about something like the triangle shouldn't be a line or something
maybe there is some issue that we don't include
no only the condition I told you
since the 9 6 15 triangle is basically a line
oh
what
but all of these say greater only
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bruh
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It must be only greater than the third side
If it is equal to the 3rd side then it is just a straight line not a triangle
why are there some sources that say it should be greater or equal?
I guess that's the answer
I just don't get why
is that
if it's straight line then it can't be called triangle
Maybe that they consider any connected 3 lines as a triangle but as I said it is just a straight line that has a point in the middle if the sum of 2 sides equal to the third side
I kinda get it if we had just a line and 3 points and 1 segment is equal to 2 other
maybe that's what they consider as triangle?
Yeah
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it will actually lock here in a sec
kk
it gives you some time to reopen if you made a mistake
it will :)
.reopen
✅
Just ask the question
if we have paralelogram and from the obtuse angle we want to allow 2 heights how can we do that?
1 is from the angle immediately
to the top
but another one?
where can it be?
do you want me to give you photo of what I mean?
If you really need to get the height out of the obtuse angle you can extend the line above it then draw the height
I am doing it on bottom obtuse angle so 1 height would be to do on the top and another one on the right side for example?
well I will give you question of that and you might understand better
from paralelogram's obtuse angle's vertex there are 2 height's 2cm and 3cm and angle betweenthem is 30degree find diagonals
that's the condition
so how would I do 2 heigts
from 1 angle
?
would it work?
those 2 height
s
but they form 30degree angle and I don't think it looks like 30 degree
😄
cuz it's not
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I need someone to help me with thease:
Let f be a cubic function.
For each of the statements below, decide whether it is true or false. Justify the answer.
Claim 1: The graph of f has at least one extremal point.
Claim 2: All lines of the form y = ax + b, where a,b ∈ R, will intersect the graph of f.
Claim 3: If the graph of f has an inflection point for x = 3, then f'(1) = f'(5).
@past sparrow Has your question been resolved?
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@past sparrow Has your question been resolved?
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Financial Maths question:
a) Using the given information, estimate the value of the bond portfolio if the interest rate is raised to 4.6%.
b) Suppose that the investor invests his capital into this bond portfolio for 5 years and the interest rate becomes 4% in coming 5 years, estimate the IRR of this investment.
I have calculated the answer for the first part to be 472.36, I am a bit confused about part b)
we have nothing to work with
what is "the given information"?
this is what I got at the moment
I am not sure if the 4.6% interest rate is related to part(b) at all
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Can someone tell me how I solve for the problems in the box?
@faint berry Has your question been resolved?
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how to prove this set has no limit points?
it diverges, so theres no limit point the set itself converges to, but how do you prove systematically that none of the infinitely many elements in the set are not limit points?
is it like a proof by induction somehow?
consider the difference between any two terms
you'll see that it is a nonzero finite amount. so if, say, the sum up to 1/N were to be a limit point, you'd need a sequence which converges to the sum up to 1/N
it's really easy to see with integral test also btw if you are familiar with that, then you just need to consider
$\int_1^\infty\frac{dx}{x}$
Soosh
for eps < 1/(N+1), there will be no such sequence which eventually gets within epsilon of the sum to 1/N
which is ln|x| evaluated from 0 to inf and clearly has no limit
we've not covered the integral test yet
it's pretty easy to get the idea of it just reading the definition above if you wanna peek ahead
soosh im not sure why you brought the integral test in
yeah it does seem pretty clear, but I know my prof wont want me to use it on homework
they are talking about the set having no limit points, not that the series diverges
oh i should read better
is your profile pic a strokes album cover?
it is yeah
nice
knew i recognized it
hmmm okay though, i think i kind of follow your chain of logic
to be explicit about what i said above, you'll note that the closest term to a_n in magnitude is a_{n+1}
right
and that difference is exactly 1/(n+1)
um btw a_n here is the sum to n of 1/i
but anyways
if you wanted to construct a sequence that converged to a_N, you'd need to find some elements that eventually satisfy
|a_N - a_n| < 1/(n+1)
but that is impossible because of what we mentioned above
ohhh i see
you can also notice that no element of your set is the limit of any subsequence of a given sequence, and this is because the given series diverges to infinity
yeah that also sounds like a familiar theorem
that might even be easier
it comes from metric toplogy
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hello, im back
i realized that showing that each term of this set are not limit points is not sufficient to show that the set is closed.
i am lost as how to formally prove that this is a closed set.
Are there any limit points?
meaning that if a sequence is convergent...
but how can i show there are no limit points?
i put isolated points up there but i meant none of the terms are limit points
ok, here's a different approach
find the complement set
show it's a union of open intervals
okay, so that would be like (-infty, 1) U (1, 1+1/2)U(1+1/2,1+1/2+1/3)U...
oh thats way easier
is there a more clever way to write that complement though that im not seeing?
no that's exactly how you're supposed to write it
wow
ive been working on this problem for a bit and now its just going to be like 3 minutes to write up lol
thank you so much
if you want to go the alternate way of showing any sequence that converges has limit in this set
take any convergent sequence (xn) with values in this set, name it E
name the limit of that sequence x
you know x >= 1
show that E intersected with [0,2x] is closed
conclude that x is in that set, so in E
im not sure i follow
you know that a set E is closed $\Longleftrightarrow$ for any convergent sequence $(x_n){n\in \bN}$ with values in $E$, the limit $\lim{n\to\infty} x_n \in E$
rafilou2003
right
so
you wanna prove the latter statement
"Let a convergent sequence $(x_n)_{n\in \bN}$ with values in $E$"
rafilou2003
name $x = \lim_{n\to\infty} x_n$
rafilou2003
Step 1: show $x\geq 1$
rafilou2003
Step 2: show $E\cap [0,2x]$ is closed
rafilou2003
why [0,2x]?
[0,2x] is a closed set that is a neighborhood of x
any other set like that works
Step 3: find a sequence that converges to $x$ with values in $E\cap [0,2x]$
rafilou2003
Step 4: deduce that $x\in E\cap [0,2x] \subseteq E$
rafilou2003
basically use epsilon definition of convergence with epsilon = x
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Hi! I'm struggling with some surjectivity and bijectivity proofs.
My current problem is:
if $f: A -> A$ and $f(f(x))$ is bijective, is $f(x)$ bijective? Either write a proof, or find a counterexample.
Note: I am NOT looking for an answer. I would like guidance.
I've tried for about 3 hours in total now with a few approaches.
Nameless
My current thought is that $f$ must be bijective.
If we assume it is not surjective, then $f(A) \subsetneq A$. By the definition of a function, the image of a function under a set $X$ cannot have a higher cardinality than $X$. Consequently, it's impossible for $f(f(A))$ to be onto $A$, since $f(A) \subsetneq A$ and $f$ must therefore be subjective.
Nameless
I'm not sure if that's correct, and also don't know how to prove injectivity
I love discord. What the hell.
Block him…
Done already
First, is my reasoning for the onto-ness of f correct?
Yes
Perfect. Thanks ~
I was trying to show the concepts to you, but looks like you are pretty good with these already
Yeah. I think I understand the concepts. I just struggle with proof writing
Hmmm
Try this
This should destroy this question in no time
So f(f(x)) is definitely included in the example above
in this, is gf(x) function multiplcation or compsition ?
I'm not sure if you even need this proposition. If $f(a) = f(b)$ then certainly $f(f(a)) = f(f(b))$. But since $f(f(x))$ is bijective, then it is injective so we have that $a = b$. Right?
Awesam
I had that $f(f(x_1)) \neq f(f(x_2))$ when $x_1, x_2 \in A$ and $x_1 \neq x_2$.
If $f(x_1) = y_1, f(x_2) = y_2$, and $y_1, y_2 \in A$, then we have
$$f(f(x_1)) = f(y_1) \neq f(y_2) = f(f(y_2))$$
I decided this was wrong since we don't know that $f(x) = y$ where $x \in A$ necessarily outputs all $y \in A$. The knowledge this holds for all $y$ is part of the definition of injectivity.
Nameless
This seems like simmilar reasoning to you, @fading dock ?>
OH! Since I have shown the surjectivity of $f$, all $y$ are necessarily outputted. Consequently, this holds for all $y_1, y_2 \in A$ where $y_1 \neq y_2$, thus showing injectivity and therefore bijectivity of $f$ ??
Nameless
yeah I think that reasoning holds after you have shown surjectivity as you figured out. it's kind of similar to what I said just coming at it from the opposite direction
I see. You're showing that $f(a) = f(b)$ for all $a, b \in A$ where $a = b$, where I'm showing the not-equal version of the same thing
Nameless
yours seems significantly simplier though
yeah you just showed the contrapositive of what I showed
also I didn't exactly show that $f(a) = f(b)$ whenever $a = b$. what I showed is that $f(a) = f(b) \implies a = b$, which is logically equivalent to $a \neq b \implies f(a) \neq f(b)$, which is the definition of injectivity
Thanks both of you. I appreciate the help
Awesam
I see! I've been operating on a slightly too strict version of injectivity, then. I conflated $f(a) = f(b) \implies a = b$ with $$f(a) = f(b) \iff a = b$$
Nameless
wait. i was wrong in the above message.
a = b \implies f(a) = f(b) is trivial and holds for all functions.
I'll have a think about what my confusion actually was, then.
thanks again.
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Im a bit stuck on this
could you explain what part? it seems you have it pretty much solved
I understand a bit since thats what we've been doing all week but im stuck on is minimum and the range
ah alright
so does it have a specific minimum
and there's your answer
for both of minimum?
what y-values does the graph exist on?
so, looking at the graph, where does the function exist and where does it not exist with respect to y-coordinates
1 and oo?
I think you get it but it's negative infinity to 1
Oh because it starts from the left side I see so like this (-oo,1)?
we're referring to y here so we think about it from down to up instead of left to right
so when you start from the bottom
that's negative infinity as you established
and then it stops at 1
yes
there's no minimum
its -infinity but the minimum is looking for a value so it's just DNE
Got it but I can ask we do one more to see if i got it?
sure
yeah
yes
yeah
does that matter here
Oh so -oo,oo?
yep
Im not sure I don't think so because its not intersecting with it
would it be oo?
Are you still there?
I figured it out but one of them I got wrong
Yes
oh I didn't put anything in yet
Yep
Im not sure thats right
ah awesome
Arightyo I might be back later on but thank you 😄
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can someone help me with 3
i love you
but i can’t help
i’m flirting with a girl
this is a one time moment for me
💀
I would first combine the denominator so you just have a fraction on a fraction. Then use the rule where you multiply and flip the second fraction.
would this be correct?
correct so far
what would i do next?
Divide both fractions
im confuse how would i divide them?
Do you know how to divide two fractions?
Yes
and then that turns into a multiplication sign and the second fraction is reciprocated
Thats it
would i do this
Now expand and simplify
yes you can do that
First step is to put the fraction together
so would 5x/6x-21 be the final answer?
yes
alright theres a rly hard 1 and ima need alot of help
I do not understand this method.
ight wat would u do
I would simply combine fraction in the denominator
then simplify the fractions individually in both numerator and denominator
then divide the fractions with the multiplication method
could u help me find the denominator
Sorry mate im super busy right now
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Is there a way I can learn Maths faster for my upcoming exams?
There is no shortcut. practice textbook questions with fully worked solutions, followed by past papers
are there any resources you can recommend?
You have not specified year level or topic
IGCSE Additional Mathematics
The topics that are a challenging are circular measure, combinations and permutations, trigonometry
pnc is all about practice
trigonometry is learning formulas
now idk what is circular measure
everything about circles (sectors, segments, archs, etc.)
I am not familiar with IGCSE. I am familiar with HSC. I think you might be interested Terry Lee. https://advancedmathematics.com.au/products.htm. For your case due to syllabus changes it will probably be best to go libgen and see if you can find an old textbook that covers circular geometry
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you found the critical points but one of them corresponds to a local minimum and the other corresponds to a local maximum
you need to identify which is the minimum
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I am graphing systems of linear inequalities to find the solutions.
I run into a problem where i get the correct lines but when filling in. (you fill in the area to the graph that satisfies both inqeualities)
My question is :
When you change inequality into a temporary equation.
If during the simplification of the equation you have to multiply the equation by II *(-1)
do you change the >,< behind the scenes?
example:
x-y < -5
x - y = -5 II -x
-y = -5 - x II * (-1)
y = 5 + x
I can gather the info to the line from here but when testing witch side of the line gets filled in the test is:
Substitute x,y with a point (0,0)
y < 5 +x
0 < 5+ 0
0 < 5 TRUE
Or should i have changed the < from the original inequation into > since we multiplied by -1?
you can do the simplification with the inequality itself
x - y < -5
x + 5 < y
y > x + 5
but yes if you multiply -1 you need to change the inequality sign still
Okay! So in a way i could do the whole process without changing the inequality into an equation and then i would keep better track of the state of : <,> ?
yes
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Just put limit x tends to 1
If x>1 then it'll be the right hand limit
If it's <1 it's the left hand limit
All of them should be equal to what the function equals at x=1 to be continuous
@floral compass Has your question been resolved?
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Hi can someone help with this? Looks impossible without negation operators
Start by turning for all into there exists, and there exists into for all
If you want to disprove something is true for all x, you just need a counterexample
You need only one example to show that the claim is false for one particular x
Ok so I have now on paper “for all y being an element of the real number, there exist a x being an element for the natural number set”
$\neg \forall x : p(x) \equiv \exists x : \neg p(x)$
tales
What does this mean?
'-'
Ok that’s true
That's the negation of forall x
This????
In plain English, the negation of "for all x, P is true" is "for (at least) one x, not P is true"
There exists an x where P isn't true
Does that involve using conditional or negation operators? The question said I can’t use any of that
south
Yeah, like south said
Stuff like that ye
I’m lost..so like right now; I’m here.
What do I do next?
.
The equivalent part on the right is the statement I need and it doesn’t involve the use of conditional and negation operators?
Ohhhh
I get it
Hang on
What about the z part? “There exists a z part of the rational number set whereby xyz >0”?
Do I just xyz<0 and it will suffice?
<=
Or do I need to change the statement in front as well?
You need
I change it to “ for all z part of the rational family, there exist xyz <= 0”?
Like that?
Is that right?
seems correct
