#help-38
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@sleek quail Has your question been resolved?
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you didn't set up your equation properly
🤔
since you don't care about the quotient, only the remainder,
remainder theorem would be less tedious
it looks like you ignored the equal to the square of the remainder when...
you just set the remainders equal to each other
try write what the property says
So do the question again
So like i use the equation divide by x-1 and square the reminder?
... = square of other remainder
instead of
= other remainder
Like that?
poor wording
,rotate
no
Emmmmm
-3?
no
Oh
Ok i think I should do it again, the question so now i do the same thing, but when i set the question
I square the x-1 reminder
Sry🥲
i actually don't see how you got
3 + a+ 1
for the remainder when dividing by (x-1)
but it is the correct remainder
since you don't care about the quotient, only the remainder,
remainder theorem would be less tedious
you can get the remainders simply by plugging in x=-2 , 1
I think I got it
Tyty
I got a other question
Question 49, my idea was synthetic division 2, and -1 figures out both reminder and set them equal to each other, and plus a other 12 to the “2” reminder side
Is my idea make sense or is it wrong
<@&286206848099549185>
Oh shoot
Then use the multi choice I think
The remainder
Let me try it again
Yeah
-b+a+8
Remainder for 2
What’s that
How did u get that
Last one was b+2a+4
Multiply by 2
Is 2b+4a+8 but subtract 5
(5 being constant
So
2b+4a+3 is remainder for x-2
Don’t rely on Me lol
2b+4a+16
-5
Yes
-b+a+8=2b+4a+11
Yes
(Sorry I’m on my bed rn so I’m just doing mental math)
Is fine lol
Is fine
Ok
I mean what if we don’t have the multiple choice
-4=b
Cuz on test I don’t think we do
Idk our teacher just like that
I think we should plug like (-2,31) in to the equation.
Technically it can be like -5=b and 4=a
Yeah
Yeah
@zenith bane Has your question been resolved?
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the answer should be -100.8 but im getting -170.8. i cant find the error
2nd last line first term
28/12 * 6 should be 28/12 * 36
also tbh you have made your own life harder than it needs to be
oh i see
how so
is there an easier way of doing this
well yeah like you could have written the inner integral as $$(4-4x)\paren{\frac{7}{6}x - \frac{7}{10}x}$$ rather than have to drag 4 terms after yourself
Ann
and then this can get simplified a bunch algebraically
like $4(1-x) \cdot \frac{7}{30} (5x - 3x)$ or something
so that you end up with $\frac{14}{15} \int_0^6 2x(1-x) \dd{x}$ which is less heavy
i think you missed an x
yes i did my bad
this actually makes it even simpler cause you can now pull a 2 out as well
oh i see
yeah that wouldve been easier for sure
ill keep that in mind. thank you
moral of the story is dont burden yourself with more arithmetic than necessary
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wdym
y = -√x
Is this what you want?
I don't think I understand your doubt
Also, lines are infinitely many, so what do you mean with linear graph?
dk what your question is
but y = sqrt(x)
if you send x to x^3
then the line is above the "radical graph"
,w graph y = sqrt(x^3) and y = x for -1 < x < 2
radical graph but only one degree inside it
then it's not possible
between 0 < x < 1
x^(1/2) > x
u can translate it yeah
but it's not going to be under the linear graph
the line can be tangent to it
or the "radical graph" can be totally to the right of the line and not intersect
something like
,w graph y = sqrt(x - 0.75) and y = x
well if you do the same transformation
then you can always define a new variable
v
v = x - c
then you have the same y = v and y = sqrt(v)
so the same situation
as this
hm ok...
sure
anyways tysm blesss
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Can someone help me simplify the following
observe that 11 + 2sqrt(30) can be turned into the form (a + b)^2
yeah
we wish to turn 11 + 2sqrt(30) into the form a^2 + 2ab + b^2
Ok
i believe you are astute enough to know of course the 2ab term will be the 2sqrt(30)
about what
well you try to match your a and b to the required values of their sum and product
But why not other numbers like 7+4 or smth
7*4 isn't 30
they are similar
can you elaborate?
is that an S or a five under the inner root?
well, turn it into the form a^2 - 2ab + b^2
to make the expression a bit clearer to you, you can move a part of the 8 into the square root; in particular, 8sqrt(5) = 2sqrt(80)
so is it like the previous:
Where:
- a-b=21 ?
no, the minus sign should not matter in your system of equations
it's essentially the same idea; find a, b such that ab = 80 and a + b = 21
how'd you get ab to equate 80 ?
it's a bit of a shortcut
Could you tell me ?
you want to find ab such that ab = sqrt(80), so a and b may be in square roots. but i recycled the notations by letting a and b denotes the number inside the square root instead of the roots themselves
with this we have a simpler system of equations here, the terms for your (a + b)^2 shall be the square roots of the system's solutions
but like how does ab= sqrt(80) ?
well you want to turn 21 - 8sqrt(5) into the form a^2 - 2ab + b^2
yeah
so we have a^2 + b^2 - 2ab = 21 - 2sqrt(80)
if you match the coefficients, we have the following system of equations [
\begin{cases}
a^2 + b^2 = 21\
ab = \sqrt{80}
\end{cases}
]
yeah
but by doing what i said here, we have a simpler system of equations that you can solve
that is, a + b = 21 and ab = 80
find such a and b, then plug it back into (a + b)^2
note that the a and b in the system of equations and the a and b in (a + b)^2 are not the same thing
in particular, the latters are the square root variants of the former
Yeah, I understand all of this.
My, doubt
is that how would you go about converting 21=a^2+b^2
like how would you solve for a, b
yeah
(Also sorry for wasting your time)
how do you find numbers for the variable to equate the statement ?
usually the numbers are simple enough for me to do it in my head
in the events they are not, there are methods that i think is not relevant to you at the moment
in school
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how does this simplify?
Multiply all the terms in the denominator by a
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hello
is this formula correct for getting the variance of a sampled group data
What’s the f for
Do you have more context
for example we have a table of grouped data with each class and their midpoints and frequencies
trying to find the variance of the sample
n = number of data values
f = frequency
Xm = midpoint
i know that this version is for non grouped data
@halcyon harness Has your question been resolved?
@halcyon harness Has your question been resolved?
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technically you can use lhopital but it's not the best way
try using cosA-cosB formula
Thats what the solution says and it ends up doing a roundabout into taylor expansion
Both methods seem meh
taylor expansion?
i dont think you need that
after cosA-cosB you can use sinx/x result to simplify the limit
Yeah...
try cosA-cosB
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Why did you square the 3x?
Cuz i didnt know what to do with the encircled 2
Try rewriting it like this, and move the 1/2 to the front
2 and 2 cancels out?
Yep
Try to make 1 as a base 3x log
And just square the sqrt54
Using the law of logarithms
There's many ways to do logs
@nimble bolt Has your question been resolved?
This one alr?
Got it 👍
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Can anyone explain this to me? The questions is Prove 120 divides n^5 - 5n^3 + 4n for all values of n
Also is that pascals rule? I have no idea how they turned the polynomial into that form
$$ \binom{n+2}{5} = \frac{(n+2)!}{(n + 2 - 5)! 5!} $$
StrangeQuarkAL
Yeah
$$ 5! \cdot \binom{n+2}{5} = \frac{(n+2)!}{(n + 2 - 5)!} $$ = (n + 2)(n +1)(n)(n-1)(n -2) $$
StrangeQuarkAL
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ohhh shit yeah
yeah yeah that makes sense
Ah but wouldn't it be .1/5! ?
Oh wait no mb I get it
Epic
thanks bro
No problem
.close
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💀 what do i take median class as
but do i take median class above 45 or 45
45 is between 40 and 50
but 45 is n/2
not median
o wait
but i see some answers say median class should be the cf which is greater or equal to n/2
median index is (n+1)/2
dk what that is
same as their step 3 here
oh your n=90
so you use the median is the average of the middle two numbers in step 4 ^
@verbal breach Has your question been resolved?
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What do I do
@abstract junco Has your question been resolved?
@abstract junco Has your question been resolved?
you should put a bit more effort into the diagram, tbh. It's basically impossible to see anything there
anyways, your parabola has directrix x=-5, so it will be of the form x = ay^2 + by + c
you know that the equation holds for x=7 y=1, and for x=-2 y=13, since you're given two points
since both circles are tangent to the parabola, to each other, and that the parabola passes trough the center of the circles, you also know that the focus needs to be at the intersection of the circles
having the focus, you also know that the point midway between the focus and x=-5 will be the vertex of the parabola
which gives you a third point for the equation. Solve the system for a, b and c @abstract junco
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how do i do A in this
the waiting times have been given as a range instead of discrete values
so you'll take the mean of each class to find the estimate of the mean
i dont know how to interpret it into a mean
so from 0<x<=10
5 would be the mean right
so we just assume the value to be 5
for 10 to 20 we assume it to be 15
Yeah I get that
and we do the same thing for all the classes and carry out the standad way to find mean after that
it will be an estimate and it will not be accurate
I don't know how to find the mean from that
(mean of waiting time)*frequency for every class
add them up
divide them by sum of frequency
so the cumulative frequency is 100
so the sum of waiting time / 100
no
take the mean of all the waiting times
for example for 0<x<10 the mean is 5 and frequency is 2
so we can assume 2 people waited for 5 minutes
for the next one, 11 people waited for 15 minutes
and so on
so you find the total time all of these people waited by doing multiplication as follows:
2x5
11x15
and so on
for all the frequencies given
then add them up
Then divide by 100
yep
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i need help with geometry. Theres a right angle trapezoid abcd with diagonals that are normal to each other so that ab and cd are parallel to each other. Prove that ac * bd >= 2* ab * cd
What have you tried so far?
@flint rock Has your question been resolved?
ive written what the sides are equal to using Pythagoras theorem, but i have no idea what to do from there T-T
I'm trying to imagine this geometry. Is this the one?
yup
this is where im at rn
i named the point where the diagonals meet F
do you have any idea?
@flint rock Has your question been resolved?
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how do u do this?
It's asking for the zeroes. Where is $f(x)= 0$? (Hint: use the information given).
mathisfun
yeah but i dotn know how to actually figure it out
is (-2,0) one
Yep
is that it
No
The problem is giving you two characteristics about the function. One is the interval with respect to x and the other is if along that interval, the curve is above the x-axis or below the x-axis.
imagine you tried to draw the graph. how might that look like
They gave you the intervals of where it is positive and negative
We know negative is below the x-axis, and positive is above the x-axis, when the intervals are told to you, they are pretty much telling you when the function is below and when it is above
We would want to focus on the ends of those intervals, since that is where we can figure out it changes
The reason (-2,0) is a zero is because for the interval with -2 as a starting point and -2 as an ending point, one of them was below the x-axis (f(x)<0) and the other was above (f(x)>0), meaning for that to happen, it must have passed through the axis to switch between, intercepting the x-axis in the process
The intervals may look similar to how point are written, but just to clarify, the first number represents the starting point which is smaller, and the second number represents the end point which is written to be larger, and it means all the numbers in between those start and end locations on a number line
@mint agate Has your question been resolved?
is it -2, 0, 2, and 5?
also
Yep.
the point A (1,-2) lies on function f(x)= x^3 - 3x, determine if point A is a local max/min using rates of change
how do u use rate of change in this
i owuld just
use a table of values
or smth
Pretty much.
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need help
Can you test each out?
Check it again.
Try it with, say, a quadratic.
Yep.
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Can someone explain how they go from 2->3 in this proof? Mostly why they need the gN(g^-1)^-1?
define $g'\coloneq g^{-1}$. then $g^{-1}ng=g'ng'^{-1}$, which implies $g'ng'^{-1}\eqcolon n'\in N$ is an element of N. from there you can rewrite n as $n=gn'g^{-1}$ proving that for some arbitrary $n\in N$, $n\in gNg^{-1}$.
esca
@real herald Has your question been resolved?
theres really not much that can be explained unless you articulate what it is youre having trouble with
@real herald Has your question been resolved?
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.close
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Heyyoo, I want to create a term that can be used to calculate if an ISBN number is correct. I want to use ∑ (i=1→10) and multiply it by the individual digits of the ISBN-number. Is this possible with a normal calculator?
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What’s the difference between dS, dA, dr in vector calculus?
For example greens formula uses dr but divergence theorem uses dS, I don’t really get the difference
greens formula is for curve integrals right
or line integrals I mean
And then divergence theorem is double integrals
I’m just a bit confused by the difference
greens equates a line integral to a double integral
Yeah and then the double integral is integrated over dxdy
Or whatever variables
But then when we take double integrals in like stokes or divergence dS is used
yes
You might want to ask in topic specific channel
since u have less of a question
and more clarification/understanding
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in the first place, i do not understand what is a "projection" of a vector over another
and why it is a numeric value
@fresh mesa Has your question been resolved?
<@&286206848099549185>
do you know the formula for the projection of a vector along another?
i dont know
you are finding the y-directional component of x
so, which is the projection
so it should be $|y|=|x|cos\theta$?
p(x) is the projection in my drawing
therealtdp
Projection is along a vector.
not |y| but your projection
the projection of a vector A on a vector B is given by B.A/|B|
hmmmm yes yes where p is the modulus of my projection
yeah man i got it
thank you guys
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hi
you're almost certainly misusing the word "equation",
but what exactly are you talking about?
are you talking about how (x-1)^2 became x^2 - 2x + 1 and how (2x-3)^2 became 4x^2 - 12x + 9?
LMAO yesnits an inewuality
yes
ik its a dumb equstion
nope, my question is what exacly he did so i can search a utube video and learn
bracket expansion?
the key words you're looking for are "distributive law" and, if you are so inclined, "FOIL"
sure, bracket expansion should bring something up.
ty very much dear ann
if you know how to expand (a+b)(c+d) with the distributive law, you can re-derive the expansion for (a ± b)^2 on your own
This is binomial multiplication if you want to look it up.
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can someone explain to me why ax + by + cz = d is the equation of a plane in 3D?
you have two independent variables and the third variable is dependent
if you let x, y be the independent variables
you have z = (d - ax - by)/c, so it depends entirely on what x, y are
2 free variables and 1 dependent variable, and of course it's a linear combination of x, y, z
so you know it's a plane and not a line (1 degree of freedom) or a single point (0 degrees of freedom)
degrees of freedom is also the number of parameters
i’m not sure i understand how this implies the graph of ax + by + cz = d is a plane. take z = (d - ax^2 - by^2)/c. it has 2 free variables and one dependent one but it’s not a plane
well it's quadratic in x or y so can't be a plane
you can check these conditions for the subspace of a vector space
it breaks when it's quadratic, cause if you replace (x, y, z) with (kx, ky, kz), it simplifies to a different equation, so not a vector space
you get ak^2 x^2 and bk^2 y^2 which doesn't cancel properly with kz
i’m a little confused. so how does z = (d - ax - by)/c mean it’s a plane? i.e. why is it that linear combination => plane?
should I talk about the normal vector definition of a plane then
yes
south
so you fix the base of the normal at position vector r0
and then r = (x, y, z) is free to move around, giving you the locus of all such points such that n and (r - r0) are perpendicular
okay, wait, so you have a normal vector at position r0 which defines the plane. what’s r?
and n?
n is a given normal vector
r is any vector, (x, y, z)
you want a condition on (x, y, z) such that (x, y, z) is on the given plane
what is the condition?
so x, y, z are the only variables and the others are all constnats
south
okay, i get how this implies the red box. n * (r - r0) = 0 means n and r - r0 are perpendicular. what’s r - r0 though?
ah
ah, okay, i get it
yeah and if you're okay with the red box
$ax + by + cz = (ax_0 + by_0 + cz_0)$
south
we just define $ax_0 + by_0 + cz_0 = d$, since those are all constants
south
all constants on the LHS of the one just above
okay, thanks, this makes sense
no worries!!
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hi what to i do here?
the slope of the tangent line is given by the derivative
have you learned derivatives yet?
ok cool
yeah i did that a year ago just forgot
thanks
i get that thewn i just sub 3 right?
what do you have for a & b
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this one is especially valid since it's only the first quadrant that you're concerned with
And the limits should be 0 to 1 right if I'm doing x?
think so
yea
it'd be 0 to 1 for both A(x) and A(y)
and you understand how to go from the A(y) to the A(x) right
you just solve x = y^15 for y
!show
Show your work, and if possible, explain where you are stuck.
wait my bad you can't use A(y) if you want to use disk/washer
I dont think
you have to use A(x)
But there's no hole? Is there?
so it'd be $\pi \int_0^1 1 - x^{\frac{2}{15}} dx$
NahhFam
wym
Like to use the washer method there has to be a hole in the solid right? π (R2-r2)? There has to be like a big R right?
How did you get the 1 to be the big R?
y = 1 would be the top function
and x^1/15 would be the bottom function
big R is 1 since it's ontop
like in order to find the area between those
it'd be 1-x^1/15
int of that
from 0 to 1
I dislike volume questions
Wait it's still wrong 😭
this looks fun
It's a question from lumen in my homework- I don't know the answer - it just says it's wrong 😭
what did you input as the answer
0.3696 (the decimal answer correct to four decimal points)
is it supposed to be put in as a decimal? that should be right
if not then 2pi/17 would be the way you input it
thats the volume of revolution between 2 curves
our radius is from 1
this does give a more reasonable answer
so that radius that we are actually revolving is 1-x^1/15
I suck at volume lol
so its (1-x^1/15)^2 as r^2
it's still wrong 😔
do what @lament locust says
Yes!!!
sorry lol
gg 🫡
I thought I understood it my bad
No no it's okay thank you so much
now to make sure this is proper
@river cosmos find the volume of revolution, of some general curve f(x), from a to b, around the line y = d
Is this correct?
from a to b
x = a to b
but justify to me
why does this work
[d-f(x) ]^2
Because we're using the disc method and the radius is like the top function minus the bottom one (like if we take a random point)
hm
that may be the case
but what if the function is above the axis
then what is this radius
f(x) - d !
yea
now that seems very different from d-f(x)
and it is
but there is something very nice about r and r^2 that we can do
ooo what is it?
-d + f(x) ?
you might need to factor out a negative
yea#
what about this one
That's also just [d-f(x)]^2 because the negative cancels out right?
yea
(-1)^2 = 1
so both of those radiuses, above and below our axis y = d
will give us the same general radius
lets try something else though
Ooo what?
if we want to find the volume of revolution between two curves
there is some conditions involved
that being one must be greater then the other for all values in that interval range a to b
But if that's satisfied we can still use the radius thing? With the radius being f(x)-g(x)?
No wait that's a washer right?
im not too sure what i washer is
but the disk method works very nice here
not exactly since that method was used for "making y = d the axis of revolution"
but our axis of revolution
still remains as the x axis
Oh... but how do you calculate the radius around the x axis? Is it just f(x)?
But that can't be right?
Because then the g(x) doesn't come into the equation at all
so in this diagram we are gonna assume that f(x) satisfies that condition that its gonna be greater than (in y value) then g(x)
the goal is to find the volume of revolution between these two curves yea
Yeah
Do you just calculate the volume of f(x) and g(x) separately and then subtract?
im going to indicate this g(x) as little r for small radius, and f(x) as big R for big radius
yea
what is the area of the pink region
pi R^2 - pi r^2
ye
applying this to the disk method now
what should we get for that volume of revolution between the curves
?
goated
now factorise the pi
and substitute R and r with the functions
Integral of π [f(x)^2 - g(x)^2]?
yep
from a to b
but that will give
the volume of revolution between two curves, (given f(x) is greater than g(x) in that interval range a to b)
how cool is that
Very cool! Thank you so much! I actually understand this way better now - thank you for asking all the questions 😅
🫡
make sure to always to ask
the most important question of all
what if ...
- why but what if is just cooler 🔥
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Package holidays to Costa Natura are priced per person.
The current brochure only gives departure dates up to December 17th, but holidays continue after that date.
The total price per person is made up from the flight price for the outbound flight, the flight price for the flight back, and their cost for the room.
The room price does not depend upon the number of people sharing the room, but may change from week to week.
The flight price changes frequently, but is the same in both directions on any date.
There are no discounts.
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Someone has put a coffee mug on my brochure, and I can't read some of the figures.
Please don't occupy multiple help channels.
what is the question?
!1c
Please stick to your channel.
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Wolfram even gives it into the same form
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If any1 gets to this
Please dm me..
Just to confirm answers
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i am confused about my professors lecture, need some help understanding something
,w graph 3x^3 - 9x
the function is Z -> Z
yes
this function isn't injective if it was R -> R
but for Z -> Z it looks like it might be
oh then it isn't
thats what im saying !
,calc (3(-1)^3 - 9(-1))
Result:
6
,calc (3(2)^3 - 9(2))
Result:
6
yes isn't not injective.
is my prof just wrong ??
this was a like take home question he had all day to think about it
yes, its not like they don't make mistakes 
gg
he mentioned later on
its surjective if m does not divide n
but i dont rly understand that part either
what is m what is n
m is 3 in this case and n is 9
and what is the overall context
are they referring solely to functions of the form f(x) = mx^3 - nx ??
well if m and n share a divisor that isn't 1
then clearly this function cannot be surjective
so if gcd(m, n) > 1
why tho
then the function isn't surjective
because f will always be divisible by the gcd
in particular, f(x) will never be 1
====
As for this claim
I'm not sure it is true
and I don't think it is
if m is very large compared to n
then this function grows in magnitude far too quickly
for it to possibly hit small y-values
you can write down a more concrete proof with some counterexample, but yeah
so this sounds like bogus.
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Do we know how we find range and domain through graph?
yea i think? domain is x and range is y'
Domain is just the numbers that a function takes in. Range is just the numbers the function outputs.
So what numbers are taken in, and what are outputted?
Domain is values of x that are valid to be use in it, and range the corresponding output
That is not correct notation. Make sure you order it correctly.
order?
Why do you say so?
mathisfun
If that is what you mean.
It means the point is included within the domain/range of the function.
above the 5 right?
Yes.
^
Do you know the notation for a number included within domain/range?
so is it (5,10) and (-infinity,5) ?
notation im not shure what that means :,c
(5,10) less than or equal to?(-infinity,5)
Unsure of the word "notation" itself, or don't know the notation?
Is this all for domain?
i just need to find domain and range for the first one
for domain i pout - infinity,5
put*
(With a closed bracket at the end.)
$(-\infty, 5]$
mathisfun
Represents that the value is included within the domain/range.
Eh, not really.
?
"Is there any moment when graph goes to y = -5" @near flax


