#help-0
1 messages · Page 602 of 1
From point c and down
Yes
a is?
a is (22-12)/2
the base or
22-12 gives you the extra width
Which is split between the left and right side of the trapezoid
Keep it as square root then
ok
Aye, it seems like this room is clear?
Working on final review stuff, can someone help me understand this?
Brain is kinda blanking, I haven't done this stuff since the beginning of the semester.
I know that 2x-3 and 8-x are both their own function lines
nyet, from what I can remember, you just pick for instance 4 values greater than 3, then plug them in
and that is the x value, the equation it gives is the y value
First two points that I would pick are 3 for both 2x-3 and 8-x
Label those points first
then add two more other points
Shouldn't matter which.
You can't pick 3 tho right?
Its x is greater than 3 for one.
You can for 8-x of course
You can still use it just not shade it in
This will be useful when you are calculating the limit.
because it'll be from where they are not continuous?
yeah
that means it is undefined at that point.
So you could do this, or if not, pick another point.
It is up to you.
Okay so first equation set would be (3, 3), (4, 5), (5, 7), (6, 9)
Second would be (3, 5), (2, 6), (1, 7), (-1, 9)
(3, 3) however is not a valid point, so make sure you don't shade that point in.
Yeah
So yeah
Got what you got
So now the question is the approaching limit thing
I know that x approaches 3- is from the right to left iirc
Then 3+ is vice versa
does it?
We are approaching the function f(x) from the left side.
Which function is used for left side of 3?
Second one I believe
Yeah x<=3
The function decreases
We don't care about that, we care what value are we approaching as x approaches 3
5
So the limit as it approaches from the left is 5
Then limit approaching from the right is going to be before the undefined point right?
Because (3, 3) isn't defined
Well, yeah it is undefined but we don't care about that.
So you're approaching 3?
So a is 5, b is 3
It looks like we are approaching 3, but we don't actually. But this doesnt matter since limit is all about approaching.
yeah
So now what is c)?
Well, for a limit to exist at a point C, then its left hand limit and right hand limit must be same.
Is it the same in this case?
Yeah
SO IF the limit approaching from both sides was continuous
Or well
I guess it wouldn't be continuous
Right?
Or would that be going into the approaching positive and negative infinity.
Well, if the limit on both sides were same, then the limit would exist at that point.
this would have limit
Go ahead, give it a try.
Because its undefined at one point right?
It is undefined but if we just look at limit, it looks like it is approaching same value from both sides.
So in fact limit does exist.
However, the function itself is not continuous.
Yeah makes sense
Idk why but mathematics books have always been in my experience horrible at explaining concepts
At least higher level ones anyways
Ah well,
Also so when it says label at least 4 points
That isn't really needed right?
In this case
They just want you to graph it basically.
Like you could literally just graph 4
for both
and you'd have your answer
or 4 and 5 for one and 4 and 3 for the other
so
both equations are (4, 2)
With the one for 10-2x not being defined
but as its approaching, it would still be 2
so in this case, wouldn't all of the answers be 2?
yeah
Yeah, that makes more sense now
I'll write it down that way where its just talking about the maximum y value as x approaches what number
This was more of a pre-question for the one I had, which is finding limits for more complicated limit equations
So like, if its as x approaches -2, if you think of it graphically, it would be when that equation is approaching -2
So would you set the equation to -2 and solve? or could you set x to -2?
first factor out both numerator and denominator.
$x^2+3x+2 = x^2+x+2x+2$
zslya
similar idea as well to the numerator
What confuses me is it looks like you just split 3x into x and 2x
factoring always confuses me because I don't know why that happens
Practice more and it should come to you naturally.
For 2x^2 + 4x?
2x^2+2x+2x+4
You mean group it with the numerator? Or
@shadow sparrow think about which two numbers will yield a product of 2 but a sum of 3
no no I meant factor the numerator lol.
I conceptually get that idea, its just always confusing how you pick what the factors are based off of
Because in this case its 3 and 2, but in some cases of more complex factoring, it gets confusing for me
Like I said, practice.
Like I know you have to have two values from the equation and then find the product of one but a sum of the other
Yeah u need to practice
Where would I practice factoring? Is there a good website for it?
I can do so after finals more specifically
I would just google it and see if there are pdfs for it.
^
So $x^2+4x+4$
Huntifer
Yes
$\frac{(x+2)(x+2)} {(x+2)(x+1)}$
yeah
Yes
zslya
Oh yeah hur dur.
Huntifer
Huntifer
hold on
,w
,w ((-2+2)/(-2+1))
So undefined
Yeah
It's 0
0/1 is a number
Sorry, brain was being dumb
So in the case of basically all of these
would you pretty much just factor?
Unless it was simplified enough to just test the limit
if it's 0/0 when you plug in then you need to do something
No
-1 and -7
They are easy
(x-7)(x-1)

lol
please don't give answers directly (if you are)
When I'm looking at factoring, I'm thinking of looking at the numbers in the equation
so in the denominators case, -6 and -7
the numerator/denominators are quadratic
you need to write them as a product of linear terms
that's what we mean by factor
uh
Okay
mm
So I know the leading term is x^2
arent you looking for the roots?
in the case of a quadratic
That being what two numbers when multiplied will equal one term, and added will equal the other.
what are you factoring?
So factor the numerator first.
-8 and 7 right?
Break apart 8x like I did on previous questions
I'm not saying -8 and 7 are the roots
I'm saying you see what multiplies to -8 and adds to 7
I think that was what they misunderstood before
Yes
so yeah, -1 and -7
that makes sense.
Because -1 and -1 added is -8, multiplied is 7.
so (x-1)(x-7) is the numerator
added to -6 and multiplied to -7 would be uhh
1 and -7
so (x+1)(x-7)
Or wait no
other way around.
Sorry lmao
what do you mean other way around
We multiply them back again
?
lol
urgh
Lol
So wait
don't troll plz
Would it be (x+1)(x+7)?
or (x-1)(x-7)
To clarify
In relation to the numerator
Which ones give u -8 when u add them?
If you're unsure you could always expand them by multiplying and see if it matches
It's the second one
Okay
So in the case of it it was 4 and -8
It would be (x+4)(x-8)
Just clarifying so I know
Which question is that
So in the case before it'll now be
if you are unsure of your factoring you can multiply to check
$\frac{(x-1)(x-7)}{(x+1)(x-7)}$
Huntifer
how to solve for the top part
@obsidian badge If this is another question, channel is in use, please read #❓how-to-get-help
k
Make sure to check the message time to see if its recent when asking for help
thats what I do
Anyways, so
$\frac{((7)-1)}{((7)+1)}$
Huntifer
Yes
Okay, so I next one, this one is different
Approaching 0 from the left side
So negative to positive
Factor x^2-2?
Remind me, do you mean expand the numerator or cancel it with the denominator?
PBj4FPxrZF7ovZ
So you're canceling one of the x from the numerator and denom
kk just wanted to make sure I was understanding right.
Same thing you do with another older equation iirc where its like n(n^2-8x)/n or whatever it was
then you cancel the numerator with the demoninator for n^2-8x
So its as the limit approaches 0 from the left..
So would you set it to 0? or like -1?
By adding something to the equation and the limit?
x²/x - 2/x
Division by 0?
Yeah it would just equal 0
Yes it is inf.
if its moving towards the right?
this.
$\frac{x^2}{x} - \frac{2}{x}$
Huntifer
splitting the fraction
So would I plug in 0 when I split it?
Or would I do something else with it in this case
Simplify x²/x
x
can the limit be undefined?
I guess its got to do with "formal" way of showing it?
I mean, I would also usually just plug it in and call it end of the day
oh it's 0 from the negatives
yeah if its 0 approaching from the left
It would just be the opposite infinity?
So if its heading towards the right, its +inf, to the left, its -inf
Yes
How would you know though at what point you could just call it infinite?
If that makes sense
there's a formal definition for it
But it's -2/x
that involves epsilon delta
So negative negative inf
,calc -2/(-0.0000000001)
Result:
2e+10
I guess its just mainly
like how far should I go before I know its infinite when reducing
Or actually, maybe this will help explain it mentally for me
There’s no memes channel? What about all the spicy math puns
@jade spear #chill
Pretty sure #math-discussion would be fine with them too
So for e
factor the top and buttom
Top one would be finding what adds to equal 1 and multiplies to equal -5
Denom would be adds to equal -2 and multiplies to 1?
well the second one would be -1 and -1
the first one my brain isn't figuring out for some reason
Actually, I don't think you can factor the numerator
with rational numbers
no, it's not suppsed to be factoring
try dividing the top can bottom by the fastest growing term you see
x^3
Huntifer
?
oh also thought I'd take a shot at d
Let me write up what I did
$$\frac{\sqrt{x}-4}{x-16}$$
$$\frac{x^2-4}{x-16}$$
$$\frac{x-4}{-16}$$
$$\frac{16-4}{-16}$$
Kk works
1min
how did you do that?
something looks off
is it a variable substitution?
Huntifer
Square root is equivalent iirc to a square
in respect to fractions
thats how my brain did it anyways
what do you mean?
that looks wrong
don't you have to get rid of the sqrt?
yeah, that will help to get rid of the square root
another way is multiplying by sqrt(x)+4 on numerator and denominator
@shadow sparrow factor the denominator to (√x-4)(√x+4)
how come we dont cancel out the 2x at the bottom?
The x=y^2 one sounds easier in my brain I'm guessing
$$\frac{\sqrt{y^2}-4}{(y^2)-16}$$
Huntifer
if this is what you mean
Write it out
can you simplify this now?
I honestly don't really know, I know there is an operation to cancel sqrt like this but
The denominator can be factored to (√x-4)(√x+4) then you can cancel out with the numerator
square root is the inverse of square
when I think of it I think of it like
Lol I'm talking to myself, have fun
Well
You aren't explaining it
I don't get how the denominator can be factored to that
I said that
Multiply it out, and see if it gives u x-16
can you simplify this?
Nein, I'm unaware how
Or at least I'm not confident in how
or do you mean
x=y^2
so you turn sqrt(y^2) into y
The way I think of it is
that gives $\frac{y-4}{y^2-16}$
Element118
and as x->16 y->4
Wtf
Huntifer
Where the inverse square of the root, then you square both sides
Good luck with whatever you're doing, but the answer to the limit is 1/8
I'm aware
I'm not here for just the answer
I'm here to know how, because this is a final review
I told u what I need to do m8
And I told you I don't understand how thats done
I'm pretty visual in terms of learning
So I need to go through and see it in practice.
As x approaches 16, y approaches 4
what does that mean though in this case?
I guess more so how would it translate back?
Err.. I sorta get it but I'm still kind of confused
I get how y must approach 4
So are you saying you substitute a x value with the trade for y?
since we only have y, we can write this as a limit as y goes to 4
so its y goes to 4
instead of x goes to 16
for the solving of it
?
So like you would substitute 4 instead of 16
Results in 0/0
probably time to do some factoring
Huntifer
and I'm not sure if thats right either
erm
what did you do?
that doesn't look like factoring
If you factor it, would you be factoring a single value?
what do you mean?
yeah
only the denominator can be factored
oh okay
well if there aren't two numbers
its just the x value for 1 and then the other number right?
so 1 and -16
is this what you meant by the other way?
oh, well since the only number is -16
4
so (x+4)(x-4)?
so then it'd be
$\frac{x-4}{(x+4)(x-4)}$
Huntifer
guys is this question correct?
The tangent line is the limiting position of the secant line as Q approaches P.
or the secant line is the limiting position?
oh im sorry
thank you
Huntifer
I think?
therefore?
Actually, how did y become 4 there instead of 16? I'm guessing because 4^2 is 16?
1/8
I get it now, I'm just not exactly confident if I got a different problem I'd be able to do the same thing
I really just need to re-do algebra because they fucked me in high school so my understanding of algebra isn't great, but its sorta too late now that I'm doing calc stuff in college, don't have a go back button lmfao
yeah
so my options are to rationalize the equation
that's the idea of substitution
or to substitute a squared y value
well you can substitute anything
or even x-10 if you wish
as long as it equals the approaching limit right
Anyways, I'll try to practice it but I should figure out that other one we kind of cut half way
So you said to take the x^3 and divide it by the x^2
divide numerator and denominator by x^3
because for x->infinity it's easier to evaluate 1/x
not really
divide by the fastest thing you see there
yeah
See I look at that
and the what I should do doesn't occur to me
Its just factoring or reducing or something
lmao
So divide the numerator and denom by x^3
so what do you get?
Something tells me I'm going to divide this wrong
just try
just divide everything you see by x^3
I think the premise here I need to clarify is
what to do when dividing with exponents
like, I honestly don't have any good grasp of how you'd do
x^5/x^3 = x^2
$\frac{8x}{x^3}$
so subtract the exponents
Huntifer
so thats just $\frac{8}{x^2}$
rokt enjr
whoops
and when x tends to inf the entire term tends to 0
maybe you can try plugging in a number to check too
Is this even further reducible though?
but 8x^2 is 100
yeah
So
x^2/x^3
Will be x^5
8x will just be 8
?
like if you tell me to divide the numerator by x^3
I think this
$\frac{x^2-8x+7}{x^3}$
Or well no
that wouldn't even be right
Huntifer
Which then you would factor the top
factoring the top doesn't really help here
So, what confuses me is
Honestly idk, you'd divide x^2 by x^3 which is 1/x
then -8x would become -8/x^2
that's multiplying
???
Or sorry
Sorry I've been doing review all day so my brain is melting a bit
So
1/x
-8/x^2
and 7/x^3 isn't reducible
Huntifer
Oh, okay now I see the fraction breakdown more
But the as approaches 0 thing confuses me
Like what I'm trying to understand is the base concept so I can apply it to different questions
as I'll have different stuff on the final I'm sure
So would this apply to basically any similar equation?
@muted hornet
Try figuring out how to find the volume of each layer and then adding them together
volume would be L x W x H in this case
where the height is just 1 unit
per layer
this would apply to questions when the limit tends to infinity
bec imagine dividing anything by like 100000000
you get a very small number right
So basically
so we say that limits to 0
So it'll only be on equations similiar to the one?
you can use L'Hospital's Rule rule here
dividing num and denom by the largest power is a problem solving technique used in questions when x limits to inf
Hi guys
Yeah..
so there are questions when you have to use 1/h
1 litre = 7 km
7* 3 2/7
Yeah or that
Ty
i hope this was not a test
Imma revise this after I'm done with my homework
$\frac{23}{7} * 7$
okay.
Huntifer
I see. Best of luck !!
oof, then you should get off discord
alright. i gtg, hope i was able to help you !!
Yep! That should work if I get any approaching inf questions
If it doesn't, oh well
@shadow sparrow What grade?
practice more
Worst I can get is a C in calc, but I was hoping for a better one.
I want a 4.0
but I don't see it happening
College
Damnnnn
Me be in school terrified of homework and u here final semester
Good luck to you too, my tip for you is
pay attention to algebra and hunt it down in high school
Well what we are learning is pretty new due to covid and all
if you go to college, it'll be pain if you don't understand algebra well
Late schedule
I'm suffering because I didn't understand my algebra well because I had accelerated classes and my teachers didn't help much
but I should have went and seeked different teachers
getting an error when tan^-1(1.153), can anyone explain?
pretty sure its because of the negative.
that looks like fun
Not fully sure though
Guys if a question is like
-7 + 14 = 8 right?
So then what will be
14 - -22 = will it be a negative integer or what?
negative is needed when solving for an angle, it should be
Yeah, I think its maybe because tan is undefined in where you're calculating it?
cosine, sine, tan, et cetera iirc aren't defined themselves iirc
they are defined when given at a value
Function of operations
Operation pretty sure
8
Everything inside the brackets first.
Oh
The () are put in place usually with negative numbers
Just so its clear the operations being used is to add the numbers still
The brackets are a secondary way to separate equations
The -7 + 15 = 8 I'm pretty sure I'm confused about 14 + -22
what is 22 minus 14?
8
A negative number plus a positive number is always going to basically be subtraction
because if you're taking the -22 and moving it towards the positive.
Ok
another way to think of it also is
14 minus 22
it goes past 0
with a remainder of 8 left over, so -8
wait
8x-8
where does that come from
left side is gonna be 8
Or actually let me try this maybe this will help explain it
$$[(-7)+15] * [14+(-22)]$$
$$[8] * [14+(-22)]$$
$$[8] * [-8]$$
$$8 * -8$$
Yes sorry
You said 8x-8 and I thought you meant the integer x, not multiply lol
Huntifer
So then yeah, -64
Okay now help me solve these
jk

If you think it looks cool though, here are the derivative rules
Apply power rule
copiously
My brain isn't contemplating the sqrts on b again
I know to use the power rule, I'm just kind of blanking
rewrite it in exponent form.
Or well, do I even need to do anything with the sqrt here?
Or just apply the nx^n-1
exponent form of that would be uhh
x^2/3
iirc
or 3/2
forgot which way it goes
differentiating: now with malaise
Hello
Is it using the difference rule or something..?
I need some help with calculus. I have to submit my homework tomorrow evening.
@alpine sable Channel is currently in use I think(?), check out #❓how-to-get-help
Thanks for the reference
$\dv{x} \qty(x^{\frac{2}{3}} - 2x^{\frac{1}{2}})$
zslya
yeah
power rule now
Huntifer

kk
$-x^{\frac{1}{2}-1}$
Not sure how to do that for the whole exponent
w/ texit
${}$
zslya
$\frac{2}{3}x^{\frac{2}{3}-1}$
zslya
pretty much
is that second one wrong?
which is
1
yes
Huntifer
What is 1/2 - 1
-1/2
Now what is 2/3-1
-1/3
Azaradichta
$$\dv{x} x^{\textcolor{yellow}{n}}=\textcolor{yellow}{n}x^{\textcolor{yellow}{n}-1}$$
I have no context, but it seems like you're doing some power rule problem, so I sent this
cool colour
$\frac{2}{3}$
You can leave it like that or bring x down since the exponents are negative.
Yeah
So they would be sqrts?
or
Like you'd change them back into sqrt
so it'd be
you can sure.
$\sqrt[n]{x}$
zslya
$\sqrt[3]{x}$
Huntifer
Huntifer
?
yes
you mean funky 
Huntifer
This is just the same thing

Try doing yourself
Yeah
Just use power rule
No
mmm
You can't distribute derivative on fractions
$$\frac{2}{x^4}=2x^{-4}$$
Azaradichta

Why?
you can bring negative exponents to the denominator, right?
You can leave it like that or bring x down since the exponents are negative.
I don't remember that
You did the same thing above
Azaradichta
You did this just above
Here we are just reversing it
Sorry, I've been doing calculus review all day
$$\frac{1}{x^4}=x^{-4}$$
My brain is kinda I think melting a bit
Azaradichta
yeah
You should relax, then.
Final tomorrow morning
The prof told us of the review less than a few days before said exam
🙃
Really bad professor this semester
:(
Book isn't very useful for explaining and we have had to teach ourselves mostly
That makes sense now that I see it
Basically online learning.
Its just inverse
nice
I've used it before, brain just forgot it existed
okay so
In this case 2x^-4 and 3x^-3
Yea
$2x^{-4}-3x^{-3}-4x$
Huntifer
So power rule now
Yeah differentiate it now

