#precalculus
1 messages · Page 296 of 1
Its talking about Sequence
i'm like 3 hours late but that's literally the least helpful reply possible @mystic cloak
where u find this exercises?
it's a standard question to get.. idk why they asked where it was from 
How can p/q be a sequence? Am I missing something?
It's probably two sequences p_n and q_n that aren't shown
Although that would make the second part a bit nonsensical
maybe talking about the sequence of cut-offs of the infinite fraction of sqrt(D)? https://en.wikipedia.org/wiki/Continued_fraction#Infinite_continued_fractions_and_convergents
In mathematics, a continued fraction is an expression obtained through an iterative process of representing a number as the sum of its integer part and the reciprocal of another number, then writing this other number as the sum of its integer part and another reciprocal, and so on. In a finite continued fraction (or terminated continued fraction...
In case ur still wondering after 4 days... to find the area of a circle u need to complete the square... in the form (a±b)²=a²±2ab+b², in this case b=2 for x and b=1 for y.
Hi geeks, I am a homeschooler who is currently aspiring to learn Maths and Physics and I know arithmetic, Basic Algebra and Basic Geometry. So I was wondering if I should start directly with a Precalculus text or study Algebra, Geometry and Trig in detail. My main aim is to get on to calculus so that I can understand Physics
Thank You
you need trig to do calculus and physics... so if you know nothing about trig then you're screwed, since you're neglecting an entire family of functions
Precalc texts will cover basic trig
Unit circle and the definition of the sinus and cosinus
Ya, exactly
and 3blue1brown is there for rescue as always
so I guess I should start with Precalc text
guys
which book or course of precalculus is good? i think in learn in Openstax, but maybe have a better options
cricket noises
this should be a good starting point https://www.youtube.com/watch?v=eI4an8aSsgw
Learn Precalculus in this full college course. These concepts are often used in programming.
This course was created by Dr. Linda Green, a lecturer at the University of North Carolina at Chapel Hill. Check out her YouTube channel: https://www.youtube.com/channel/UCkyLJh6hQS1TlhUZxOMjTFw
⭐️ Lecture Notes ⭐️
🔗 Part 1 - Functions: http://lindagr...
it should be a good foundation for calc 1 if you practice and do mock exams along with the course
idk how to approach this sum.can anyone help me
You can evaluate it directly
no 0*infinity form
nope
wat error did i do
to use lhop you need 0/0 or infinity/infinity
ohhh ok
So I need to find the range of this and give it in interval notation... Having said that, I'm not sure if the answer in interval notation would be this (-4, inf) or [4, inf), since I was only given the graph and no equation
what does range represent?
The lowest and highest y points of the slope
I believe (1,-4)
correct which shows that -4 is a possible value of the function
do u see any y value lower?
No, so then answer should be [-4, inf)
u can also look at it like this, what function does this look like?
f(x)=(x^2-1)-4
and x^2 is centered at (0,0)
u can plug in 0 and still get 0 and the range of x^2=[0,inf)
@wary mulch Just rewrite tan(x) in terms of sin(x)/cos(x) then use the product rule for limits s.t you get log(sin(x)/ cos(x) and can use l'Hopital as the expression is of the form 0/0.
this graph looks like f(x)=(x-1)^(2)-4
Got it, thank you!
[] means inclusion
() means exclusion
how can I graph a fast sketch of a fucntion like f(x) = 2/(3x-1)
yes I mean by hand
and without calculating it point per point if possible, just a general idea of what the function looks like
function transformations
this is just 1/x, with various transformations applied to it
you can rewrite this as $f(x)=\frac{2}{3}\cdot\frac{1}{x-\frac{1}{3}}$
maximo
so you're scaling it by a factor of 2/3, and shifting it 1/3 units to the right
by scaling you mean it goes up by 2/3 units?
what do you need help with?
do you know what a sequence is?
direction says "for each prob. write the first-four term"
yea
i know how to solve etc etc. but the directions are making me confuse.
i'm assuming they want you to write the first four terms of each sequence
okay how.
i know how to solve etc etc

and nth term for 10th term is 10. and 15th term is 15.
alright so let's say no
i have a book right here. but the book confuse me also. i need help with the person
so i assume replacing the n of 10 or 15?
no
but the nth term is 10 and 15.
$a_n$ is the nth term in the sequence a
maximo
what's your native language?
ang pagkakasunud-sunod ay isang order na listahan ng mga numero na sumusunod sa isang karaniwang panuntunan
im guessing you used a translator?
yes
it doesnt translate better.
"a sequence is an ordered list of numbers that follow a common rule"
"ang pagkakasunud-sunod ay isang order na listahan ng mga numero na sumusunod sa isang karaniwang panuntunan"
from either of these
do you understand what a sequence is?
yes. the sequence is ordered by the list of common that follows the common difference?
term is following the common diff, solving for the next upcoming terms?
maximo
this is a sequence $a$, the nth term is $a_n$, which means the 1st term is $a_1$ the 2nd is $a_2$...
and so on
maximo
so for the case of n=1, the 1st term, we have $a_n = n \rightarrow a_1=1$
maximo
does that make sense?
yea i know nth term is based on a1 or opposite
so what's the 20th term of this sequence?
$a_n = n$, what's the 20th term?
maximo
okay brb
wait no
the problem is incomplete tho
wait the nth is 1right?
@steel venture
the nth term is n
wait can we do like a real problem on arithmetic like theres an common diff
oki.
so one more time, if we have $a_n = n$, and $a_1=1$ is the first term, what's the 20th term?
okay so whats the formula. is it an=n or an=(n-1)
maximo
no need to be sorry
what's the 20th term?
let me know when you have an answer, it doesn't matter if its right or wrong
i just want to see where your head is at
okay back
im confused at the formila
formula*
not sure if this is correct or not.
im sorry if its wrong.
why are you using common difference again
okay. show me the real answer
the nth term is equal to n
so the 3rd term is equal to 3
and the 15th term is equal to 15
and so on
do you see what im saying?
wdym?
ok so in the sequence $a_n = n$, what's the 50th term?
maximo
assuming the first term is 1
you got it right, it was 20
it is 50
for the nth term in a sequence, you just need to plug in the n value into the formula
so for example
$a_n = n$ for the nth term
maximo
maximo
so if i ask for the 100th term, what is the value of n?
100
maximo
what's the 1st term?
1?
yup
its up to you
okay
it's based on the formula
so what would the 2nd term be in that sequence?
get another value term?
remember
oof
$a_n = n^2$
uh
maximo
we're looking for the 2nd term
what is the value of n then? (if we're looking for the nth term
oof sorry having problems in wifi
5?
wait sorry,can we continue this later. i gotta eat.
sure
4
why
because the 2nd term is the nth term when n = 2
2^2=4...
what is that?
so, what's the 5th term of the sequence $a_n = n^2$?
maximo
a15=n2
a15=15^2
15th term = 225
why did you do the 15th term
so what's the 5th term
a5=n2
a5=5^2
5th term = 25
is it correct??
maximo
what are the first 3 terms?
np
$a_n = \frac{1}{n}$
maximo
what are the first 3 terms?
1,2,3?
i see one nth term and another nth term but half with 1
what?
what
maximo
what are the first 3 terms here
10?
how did you get 1 and 4?
the 1 is the 1st term, because 1^2 = 1
the 2nd term is 4, like you said, because 2^2=4, like you wrote
now what would be the 3rd term?
remember how you found the 5th term?
32?
OH 15TH TERM?
i want the 3rd term
wait no
but you find it the same way you found the 15th term
1,4,3?
remember, the sequence goes 1^2, 2^2, 3^2, 4^2, ... n^2
What's $3^2$
cpl
Answer my question
18
That's wrong, but how did you arrive at 18?
Depending on the contents of your math class, not knowing how to square numbers is not the end of the world



what can i do about the square root when it is subtraction
nothing, you just subtract it like normally how you would subtract two functions
@sharp lagoon depends what you mean by fg
(fg)(x) srry i wasnt clear
would that just be multiplying both functions
and (f o g)(x) is like f(g(x))
why is the answer to (f+g)(x) highlighted in green despite being wrong? 
EMM composition? am not sue
i have no idea
thats college for me
guys
anyone know the Prof Leonard precalculus class? where i can find the exercises to practice function, trigonometry and all?
you can get some from khan, or use a generic math textbook
is there a direct way to check if a function is bijective other than check for inyective+surjective?
you can sometimes just give an explicit inverse
how can I solve that?
Does anyone know where I can find the curriculum for Pre-Calc honors? I wanna see if I got the basics down
uhh probably ka precalc?
some pcalc h classes have like an introduction to limits or something similar in addition to whats in KA pcalc
Khan Academy?
if i did the check of James Stewart, i'm ready to start learn calculus 1? or will gonna be much difficult?
i need learn more something first? or i can keep going? what u suggest?
did you read the entire thing?
How can I get rid of the 1/3
Take the log
theres no need for taking logarithms
just isolate the x^(1/3) and raise both sides to the power of 3
OO THANK YOU idk why i was stuck for so long, that was all i needed!
I kept looking at it trying to figure out how the answer was arrived at. Already assuming it’s right due to the green color.
i was wondering that too LOL
just wanted some clarification.
Translation: Given f(x) as such. Assume F is the antiderivative of f on R satisfying F(0)=2. The value of F(-1) + 2F(2) equals?
So what im confused about is are they making us assume that the antiderivative of the upper branch of the function also satisfies F(0)=2? But wouldnt the antiderivative of the upper branch of f(x) have the domain of x>=1?
basically, what im saying is that the antiderivative for 2x+5 is undefined for x=0 isnt it?
or am i missing something
Is F meant to be continuous
its not listed in the question
so i cant confirm
the phrase "is antiderivative of f on R" kind of throws me off
but then again plugging x=0 into the antiderivative of the upper branch of f(x) seems kinda illogical to me. However, this is from a past national exam paper, so they must have been checked through very thoroughly, i.e its very unlikely a mistake can be found here.
Typically in this type of problem they should give you integration bounds
i suppose so too
thinking of 'branches' that way isn't sensical
oh, i didnt quite know how i would say/call it
"is antiderivative of f on R"
all this means is F'=f
how to approach this without getting tripped up by the piecewise def of f is to think of how best to explicitly define F
for all $x\in\bR$ we have $F(x)-F(0)=\int_0^xf$
Cryptic Dance of the Fireflies
hmmm interesting
never looked at it that way
oh so basically we just have to split the integral into two different bounds?
but we can be clever if $x\ge1$ and write
$$F(x)-F(0)=\int_0^xf=\int_0^1f+\int_1^xf$$
right
Cryptic Dance of the Fireflies
alright, thats something new for me
now both integrals on the rhs are easy to compute
so F is best explicitly defined piecewise as such
wait for the integral from 0 to 1, with the upper bound, shall i take the left hand side limit of x tending to 1?
since that 1 is not in the domain of 3x^2+4 right?
The problem occurs when you let x=0 because F(0)=2
And the integral from a to a is necessarily 0
strange
an alternative version of ftc lets us swap evaluations of F by limits of F
erm theres a website that has quite a different approach but comes up with the same results as yours
so many ways that we could define antiderivative of piecewise functions
by this alternative version, $\lim_{x\to1^-}F(x)$ exists and
$$\int_0^1f=\lim_{x\to1^-}F(x)-F(0)$$
Cryptic Dance of the Fireflies
right
this ensures we need not worry over computing int[0,1]f (even without this alternate version of ftc, one can intuit this is how the computation 'should' work out anyway)
you're welcome 
by any chance could somone pin the half angle formulas
in the equation $x^x=x$, the solution is $x=1$. I've been trying to solve $cx^x=x$ for $c \in \mathbb{R}$ but I can't get very far. any ideas/tips?
gmod
let me rephrase, break it into cases when c is in [0,1] and when c is not in [0,1]
how does that help? I still have to deal with the number
When is it a good time to define 0^0 =1 or 0^0 = undefined?
0^0 is undefined
well idk, that seems like a discussion-wise topic
Should I even need to worry about this for use in calculus?
I agree with that limit
So for example, Taylor series does use 0^0 = 1 in order to make the formula prettier. This is something you'll see in a calc course. 0^0 is almost never an important issue though.
<@&268886789983436800>
@fading rapids do you still need help?
hello can someone pls explain to me why the graph of the semi circle in this case is |x|≤2 and not |x|≥2
The semi circle is contained between -2 and 2
So you want to display the semi circle when x <= 2 and x >= -2
which is the same as saying |x|<= 2
np
I'm having a hard time understanding this
Why is this a thing that you can do?
Wait nevermind I got it
Feelsgoodman
any hint on how to approach this limit?
hmm. @gusty relic
\begin{align*}\left(\sqrt{x+\sqrt{x}}+\sqrt{x-\sqrt{x}}\right)^2&=x+\sqrt{x}-2\sqrt{(x+\sqrt{x})(x-\sqrt{x})}+x-\sqrt{x}\&=2(x-\sqrt{x^2-x})\end{align*} and
$$(x-\sqrt{x^2-x})=(x-\sqrt{x^2-x})\frac{x+\sqrt{x^2-x}}{x+\sqrt{x^2-x}}=\frac{x}{x+\sqrt{x^2-x}}=\frac{1}{1+\sqrt{1-\frac{1}{x}}}$$
c squared
so your original limit approaches ||1||
i suppose alternatively you could do
\begin{align*}
\left(\sqrt{x+\sqrt{x}}-\sqrt{x-\sqrt{x}}\right)&=\left(\sqrt{x+\sqrt{x}}-\sqrt{x-\sqrt{x}}\right)\frac{\left(\sqrt{x+\sqrt{x}}+\sqrt{x-\sqrt{x}}\right)}{\left(\sqrt{x+\sqrt{x}}+\sqrt{x-\sqrt{x}}\right)}\&=
\frac{x+\sqrt{x}-x+\sqrt{x}}{\left(\sqrt{x+\sqrt{x}}+\sqrt{x-\sqrt{x}}\right)}\
&=\frac{2\sqrt{x}}{\left(\sqrt{x+\sqrt{x}}+\sqrt{x-\sqrt{x}}\right)}\&=
\frac{2}{\left(\sqrt{1+\frac{1}{\sqrt{x}}}+\sqrt{1-\frac{1}{\sqrt{x}}}\right)}
\end{align*}
and see what happens as $x\to\infty$
Rationalizing and dividing both numerator and denominator by sqrt(x) might be simpler
c squared
Ye
T0lgi01
I think you can do it a bit easier:
$$\lim_{x \to \infty}\sqrt{x+\sqrt{x}}-\sqrt{x-\sqrt{x}} =$$ $$ \lim_{x \to \infty}\sqrt{x^2+x}-\sqrt{x^2-x} = \lim_{x \to \infty}(x+ 1/2) - (x- 1/2) = 1$$
The first equation is a substitution $x \mapsto x^2$, the second one is the general formula
$$\lim_{x \to \infty} \sqrt{x^2+ax} -x = a/2$$
You can prove this by turning this into a fraction and multiply numerator and denominator by the conjugate
T0lgi01
Ah I should still append the proof
$$\lim_{x \to \infty} \sqrt{x^2+ax} -x = \lim_{x \to \infty}\frac{(\sqrt{x^2+ax} -x)(\sqrt{x^2+ax} +x)}{\sqrt{x^2+ax} +x} $$ $$= \lim_{x \to \infty}\frac{ax}{\sqrt{x^2+ax} +x} = \lim_{x \to \infty}\frac{a}{\sqrt{1+a/x} +1} = a/2$$
T0lgi01
sorry for the late response but I would appreciate help
$c=\frac{x}{x^x}\Rightarrow{c=({\frac{x}{x})}^{1-x}}\Rightarrow{c=1^{1-x}$ if $x=1$ then $c=0$
leonardomoura
$c=\frac{x}{x^x}\Rightarrow{c=({\frac{x}{x})}^{1-x}}\Rightarrow{c=1^{1-x}$ if $x=1$ then $c=0$
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l.55 ...\frac{x}{x})}^{1-x}}\Rightarrow{c=1^{1-x}$
if $x=1$ then $c=0$
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@bleak relic I don't think you can go from x/x^x to (x/x)^(1-x)
by that you would get x^{1-x}
i made an error
leonardomoura
which is $1^{b-c}$
leonardomoura
you're right
so do you have any other ideas?
So I don't think this has any analytical solution like $x^x = x$. When I write the equation like
$$x^x = cx \Leftrightarrow e^{x\ln x}-cx = 0,$$
this doesn't seem solvable in general. I know that $e^x -x = c$ in general is like this, too.
T0lgi01
but I'm pretty sure you can approximate this very quickly somehow I feel like
You said you solved x^x = x?
surely cx^x = x -> cx(x^x-1 -1)=0, thus c=0,x=0, x^x = x ?
x^x = x
x^(x-1) = 1
I think c=1 is the only c for which this is easy
as long as x does not equal 0
im stuck on finding the coordinates of each side of this inscribed rectangle
i know the zeros are 6 / -6
but idk how to find the actual coordinates of x
nvm lol#
can someone ehlp
im trying to figure out the length of the sides of the rectangle
by trying to find out what coordinate the corners are on
which part are you on?
look at how the 4 coordinates are shown in the picture
those will be the 4 vertices for any value of x between -6 and 6
so now pay attention to the bottom side of the rectangle
what are the 2 vertices that form that side?
wouldnt it be 0
?
I think it has infinite solutions -> x^x-1 = 1/c. So any solutions is dependent on c
wdym
uh
try using the distance formula
sqrt((-x-x)^2 + 0)?
2x, but yeah
yes
that's for the bottom and top sides
now look at either of the sides on the left and right
yeah so what would the expression be
and apply the same idea
pretty sure c>=1 allows for exactly 2 solutions
in fact a bit lower should also work
not sure what to put in for f(x) using the distance formula
We restricting x?
what's our function?
yeah
ok
do you understand why?
yeah
I thought, given c, we should find all x that satisfy cx^x = x (or x^x = cx)
x^(x-1) = 1/c is essentially x^(x-1) = k
so for any k>0 it should have 1 solution (i think)
Plotting yx^{x}-x=0 produces something otherwise
no that's not the case (to what i said)
if you plot yx^{x}-x=0 you get a range of values for y and x
wait the height is just going to be 36-x^2 right @steel venture
yes
i plugged it in the distance formula and yeah
so the area of the entire rectangle is just 2x(36-x^2)
exactly
aight ty
c = 0.01 shouldnt give any answers x>0, going for x<0 is weird because then we have complex numbers
,w x^x
are we saying x has to be an integer or something?
how do we express the area as a function?
is it just A(x) = 2x(36-x^2)
yup
a ok
quite strange, because plotting some yx^x -x = 0 shows a graph.
If we plot cx, then if we choose c small enough, they don't intersect
i think you guys are talking about different graphs
Intuitively we can rewrite this as x^X = 1/c x = ax. So if a is large enough (as in x^x-1), it works. So there should be plenty of solutions
And like i said before, the graph has infinitely many solutions for y = 0
which *I do * like the idea of
y=0 *
^ actually very strange
x^(x-1) = 0 only has 1 solution
Incorrect actually, its just the grapher was getting too close to 0
actually i don't think it has a solution at all
Yea, my bad. The demos grapher thing was saying 0 when it meant really close to 0
ln(x) = 0/(x-1), nvm you can't even do this
wait ICSF could you explain what exactly you want to solve?
so there's no solution to the equation
to the equation x^(x-1) = 0
let's just say f(x) = x^x, yes? We want to find, given c, solutions to f(x) = cx (I just put c on the other side because I feel it's a bit easier)
if c = 1, then we have exactly one solution x=1
if c=2 then we have two solutions x=2 and x = 0.3463233622785809
Right then we have y=cx, which we can change to think of it as tan(theta)x=y. So rotating this straight line intersects y=x^x infinitely many times.
I dont think it does
x^x is continuous? y = tan(theta)x. And theta can get infinitely fine. We can intersect any angle between 90 and 0
since the derivative of x^x after a certain point is always bigger than c, there can be at most only one intersection after that
Yes but we can find a c which equals 1/x^x-1
giving by definition cx^x = x
as x^(1-x) * x^x = x = x
So you want to fix x and find possible values for c?
sounds trivial to me
you can prove that for any continuous function
thats what you are saying?
actually what I'm trying to say:
If c<1, there exists no x, such that x^x = cx
If c=1, there exists one x, such that x^x = cx (x=1)
If c>1, there exists two x, such that x^x = cx
for example c = 2 admits x = 2 (as you said) and x = 0.3463233622785809 as solutions
I see what you mean, yes
@fading rapids you got your problem solved?
not yet
oh actually I didn't realize people were having a conversation about my problem
lemme read these
thanks for providing this! but how would I go about finding such solutions without using wolframalpha
that final answer would be numerics. I can assure that one solution is in the interval (0,1) and the other in (1,inf) (open intervals). Maybe you could get an better upper estimate like c (for c>=2). Simply because no exact solution should exist, only for special cases
oh alright, thank you for the insight
what is this? @cyan cape
and you might have to take a closer pic if you need help with any
Alright @viscid thistle
Calculus,, limits
can someone help me clarify what it means to "State the number of nonreal complex zeros"
it means to state the number of nonreal complex zeros
there is no simpler way to state it
find the nonreal solutions to the polynomial
how many of them are there?
what are the prerequisites, i.e. what do I need before learning this book?
https://www.amazon.com/Calculus-James-Stewart/dp/1285740629/ref=sr_1_3?dchild=1&keywords=calculus&qid=1629069326&sr=8-3
Dude
I don't know how to describe what I'm feeling but it's the first time it was explained to me why it is like this
Not sure if this is the correct channel for this
not really precalc material
each intermediate step is justified by a field axiom or a corollary of them
where i can find some exercises to practice precalculus?
i'm studyng with this course
https://www.youtube.com/watch?v=eI4an8aSsgw&t=9064s
Learn Precalculus in this full college course. These concepts are often used in programming.
This course was created by Dr. Linda Green, a lecturer at the University of North Carolina at Chapel Hill. Check out her YouTube channel: https://www.youtube.com/channel/UCkyLJh6hQS1TlhUZxOMjTFw
⭐️ Lecture Notes ⭐️
🔗 Part 1 - Functions: http://lindagr...
most precalculus textbooks should have problems to go along with them
that's one you can use
@molten garnet no advertising.
Yeah don't post advertisements here
Or really in most servers... you should read #rules
Send invite bro
no
to late
They removed my invite so no
how do i solvew 2(x+1)(x-3)^2 - 3(x+1)^2(x-3)
you cant
wdym by solve?
i presume he wants to find x
factor
factor
factor
factor
Instead of saying factor 4 times
Just say, the problem asks to factor the expression
Also factor does not mean solve
(Just saying)
Anyway, look for the common things both terms have
And then factor it out
you are forgetting that 90% of ppl here have zero communication skills
i just took a pre calc test
and 1/4 of the test was logs
i didnt do much logs in the text book...
(im just mad cause i failed the test after putting 150+ hours and wasting my summer break)
how do i find the domain definition of this one? Ik its basic but i am not sure
It's Df = - infinity to + Infinity
there are, they're just complex.
do you know that for a polynomial with real coefficients, the complex zeros come in conjugate pairs?
i know that they come in pairs
didnt know they were conjugates
so is (1+2i) & (1-2i) the pairs?
,w roots x^4-x^3-14x^2+24x+5
that's one pair
you can construct a quadratic with those as roots, and divide your polynomial by it
...yes
,w roots x^4-8x^3+27x^2-50x+50
Please help me Solving this
what have you tried?
Can someone help me with part a of this question
I need to find how to combine the volume of a sphere and a cylinder together
do you still need help?
volume of shape = volume of hemisphere + volume of hemisphere + volume of cylinder
is the height of the hemisphere also x?
do you know what a hemisphere is?
@vagrant ingot so you don't know the defining formula for average rate of change?
oh, sorry, i'm 50 minutes late. do you still need help with this?
no i do not probably because im kinda getting ahead of thte class
and school started less than a week ago
so you're doing assignments ahead of the class, are you?
okay, so the average rate of change is simply the slope of the line connecting the two relevant points on the graph of your function
to put that more symbolically, the average rate of change of a function f(x) from x=a to x=b is the slope of the line connecting (a, f(a)) and (b, f(b))
or to put that even more formulaically to relieve you of any need for an INT skill check, it's (f(b)-f(a))/(b-a)
$ sin^4 (x) + a sin^2 (x) + 1 = 0. $ For what value of 'a' equation has solution? How to proceed. I tried substituting t = sin^2(x) but didn't reach to any result.
you will get the equation t^2 + at + 1 = 0
you want this equation to have a solution in [0,1]
do you understand why? @limpid schooner
No.
the range of sin^2(x) is [0,1]
Yes.
if t^2 + at + 1 = 0 turns out not to have solutions in that range, then the original trig equation will fail to have any solutions
i don't know what you mean by 'satisfy these value'
What to do next?
well now you want the equation to have at least one solution in [0,1]
there's a nice shortcut way to determine what a can be
and it may sound a little odd, but you can do so by isolating a in the equation.
isolating? I didn't understand the term.
Ohh. I see. I will try it
Hi everyone. I need help with a matter for which I can't seem to find a solution.
On Desmos, I am trying to do a cubic regression to find a cubic function of best-fit for a particular series of data points. You can see this on the left in the picture I have posted below. The regression works out well, as it displays a cubic graph that goes through 94% of the points, and the specific parameters of a,b,c, and d that go with it.
However, when I try to place these parameters into the general form of the equation y = ax^3 + bx^2 + cx + d, I actually do not get the same graph (see: the black graph is displaced quite far above the blue graph even though they both seem to take the same appearence)! I copied down the parameters correctly, so I have no clue what the problem is. A YouTube tutorial also suggests that you can simply copy the parameters and place them into the general form of the equation to get the same graph, but as you can see, the black graph (the equation) is completely different from what I get in the cubic regression in the blue graph.
Any help is appreciated. Thank you so much
how do i solve [-x^3 (1-x^2)^-1/2 - 2x(1-x^2)^1/2)]/x^4
$\frac{-x^3 \times (1-x^2)^{ - \frac{1}{2}} - 2x \times (1-x^2)^{\frac{1}{2}}}{x^4}$
does that look about right?
maximo
nvm i got it
pls help me
@wooden reef
what can you tell me about the slopes of lines that are perpendicular and parallel to another line?
nvm I got ty
Is this the right place where I can ask about finding domain and range?
yes
do you mean
$$y=\frac3x + 4$$
or
$$y = \frac{3}{x+4}$$
ℝamonov
-4*
The latter one
set of reals excluding -4, yes
Ok, and I can't quite understand how to get the range.
Is it all real numbers except 0?
yes
Ok, thank you!
,w roots x^3 - 1234567800x^2 + 1358022057x + 323703700758
ouch
i typed it wrong
a good way is to solve for x in terms of y and see what y values are possible
since generally, finding the domain is much easier than finding the range of rational funcs
but you also have to make sure that you cant have a y value that obtains a $x$ value that is not in the domain of the func
TheToadSage
so you cant have $\frac{3-4y}{y}=-4$
TheToadSage
this equations has no solutions, so the only real number that is not in the range of the function is $0$
TheToadSage
hii
Can anyone help me find the range of this equation? y=4x²+3x-1
Any help would be appreciated
Yeah but I cant seem to get to the answer
can i please see it?
I know the domain is all real numbers since it is quadratic
yeah
But the thing is our teacher haven't taught us about this formula, so I am looking for any other way of finding the range
-b/2a is the vertex of the parabola, which is the minimum value of f, since your function is a parabola that opens upwards
yeah, with this we can figure out that the range will be from the minimum up to +infinity.
You can also try making the quadratic a perfect square
why tho
The square part would be zero and the remaining constant would be the minimum value I guess
It's not same for every function but for some unique group of functions
if f(x)=x,
then
f(5-x)=5-x=-x+5
but f(-x-5)=-x-5, which is not -x+5
Hi i need hep in writing my answer in range
{y element R : y>=-25/16}
How can i write this in word form? like set of non-negative real numbers such that y ≥ 1
Wil i write set of all real numbers or set of non-negative real numbers?
${y \in R : y\geq \frac{-25}{16}}$
maximo
is this what you have @jovial stratus ?
if so, this is saying that y belongs to the set of real numbers, where y is greater than or equal to -25/16
Does anyone get why did we have to plug in x1=6 into equation 2 x1+3x2=12 instead of x1+4x2=24? even though B is the point of intersection between x1=6 and x1+4x2=24 and not x1+3x2=12
It might have been an error, but your right, it should have been x1+4x2=24 for finding point B.
Yes, sry for late repy
Solve the inequality x^2-4x>=0
as with any upwards quadratic there will be two intervals
you must take their intersection
how do we do this question?
nope, i haven’t learned that
you haven't learned anything about graphing functions at all?
ive only self studied graphing quadratic functions
but surely you must know the basic principle of function graphs?
surely it's not just an empty ritual to you?
like
okay, let's put it this way:
if the graph of a function f(x) passes through the point (1, 19)... it signifies that f(1) = 19.
is this familiar to you?
ahh yeah i understand that but i was never taught lol
it's really hard to believe you were never taught that.
not being taught that means not being taught how to read graphs.
i think were gonna learn it in a few weeks
it's an inexcusable omission on your teacher's side, if indeed they never so much as mentioned it.
you're going to learn it in a few weeks?
then why have you been assigned this exercise?
i think soo, since were on composite functions rn
ahh not sure :(
you're on composite functions??
yeah
then you MUST have been taught things about graphs
like cmon, this is the basics of the basics
i think we’ve only went over quadratics and thats it… i self studied the rest
then your teacher's a sham, or you didn't pay attention at the critical moment.
in any case, ok, one way or another you have the required knowledge here.
if the graph of a function f(x) passes through the point (1, 19)... it signifies that f(1) = 19.
is this familiar to you?
freya — Today at 09:27
ahh yeah i understand that but i was never taught lol
based on this... refer back to your question, and observe that you are told f(2) = 1 and f(5) = 3.
this means that the graphs of your functions must all pass through two points. can you name the points?
(2,1) and (5,3)
great.
so your job now is to draw any three function graphs which pass through these points.
as in, you should get a piece of paper, draw a set of coordinate axes, mark those two points, and then sketch three different curves going through them.
yes, so long as it passes the vertical line test
okay got it, thanks!!
How do I deriviate this function? I don't really know what to do with the 7 neither do I know what to do with the 2 above the ()
it's 7(-4x^3 + x^2 - 6x)^2
,rccw
<@&268886789983436800> you should probably delete this one too
And check the other channels for more 😄
ok there we go
Evaluate
no you
does anyone know how to rotate a graph 90 degrees on desmos
say you have the point (1,1)
to rotate it by 90 degrees you turn the point into (-1,1)
so if you have y=f(x) just turn it into f(-x)
I would probably use (0,1) as another example and that gets transformed into (-1,0) because then you know that (x,y) maps to (-y,x)
(in the (1,1) case, x = y = 1)
oh yeah nvm then i'm wrong
right because the perpendicular line is the negative reciprocal
there's 2 main things to know about problems like these
each of these functions have distinct shapes which you can sort of memorize
as you deal with them more and more it'll become second nature what functions belong to what depictions
the other thing is that you can always plot a few points to see the pattern
take the case of y=e^(-x)
f(0) = e^(-0) = 1
f(1) = e^(-1) = 1/e
f(2) = e^(-2) = 1/(e^2)
f(10) = e^(-10) = 1/(e^1)
this hints at the idea that as x becomes bigger and bigger, e^(-x) will become smaller and smaller
so the best graph in this case for e^(-x) will be the second graph on the right
you can also show that as x becomes bigger on the negative side (-1, -2, -3...)
then e^(-x) will become larger and larger in value
,w roots 6x^4 - 11x^3 - 7x^2 +8x -34
,w roots x^3+x^2-8x-6
Why is it that we can factor out an equation like 2(x+1)-x^2(x+1) by making it into (-x^2+2)(x+1) ?
I can group, I just don’t know why we can do that
Distributivity
What do you mean by that ?
The property that allows you to do that is distributivity
It is inherent to multiplication and addition
If you know how distributivity works, you can see that (a + b)(c + d) = a(c + d) + b(c + d).
We are taking the equality the other way.
Alright I understand that now, thank you
How do you do this?
Find the values of θ between 0 <_ θ < π that form the portion of the graph r = 5sin (3θ) in Q4.
<@&286206848099549185>
im so lost on finding ordered pairs on the unit circle any help?
Why can't logarithm have a negative base?
how can you solve one sided limits analytically?
and what, pray tell, do you think the limit of f(x)g(x) should be?
$f(x) \lim_{x\to0} g(x) + g(x) \lim_{x \to 0} f(x)$ is not a valid answer, as the limit is a number and its value cannot depend on $x$
Ann
really, i think you should familiarize yourself with how the derivative product rule is defined.
as-is, it sounds like you see it as nothing but a symbolic rule handed down from on high
A brief description and guide on how to use me was sent to your DMs!
Please use ,list to see a list of all my commands, and ,help cmd to get detailed help on a command!
end behavior basically describes how the y value acts as it approaches either x=infinity or x=negative infinity
so you would write it in the format of X->infinity , y-> either positive or negative infinity depending on what the y value is doing
whats the y value on this
depends on which side youre looking at
Left
well, as the x value approaches the left, what number is the y value approaching @daring wolf
X -3
not quite. so, since the image goes off the graph and continues on forever, the x value is going to continue towards negative infinity. and since the y value is also going down, IT goes towards negative infinity as well. so on that side, the end behavior is, "as x approaches negative infinity, y approaches negative i infinity
@daring wolf
So x is -infinity
<@&286206848099549185> can one of you help me better explain this
@daring wolf this is an example ... y=tanx , here at x=pi/2 y tends to infinity ... if you keep zooming out you will notice that the grpah near pi/2 will almost coinside and will look similar to x=pi/2 (so y is not stoping(as their is no finite value of y at x=pi/2) but x is const )
on the left side in ur question we can assume at a particular value of x , y will tend to - infinity
I need help with this problem f(x) = 7/1-lnx I need to find the domain in interval notation. I barely understand natural log except that it's the opposite I believe
dont crosspost
My bad
I think you forgot parentheses
But if you look at the graph of ln x you see it doesn’t take on the value of 0
Meaning x>0
Also the denominator can’t be 0
Meaning x can’t be e
Meaning 0<x<e , x>e
They got help already
Oh ok
Alright thanks
$\int x^3 \cos(x/2) \sqrt{4-x^2} \dd{x} = 0$ by symmetry, so your integral reduces to $$\int_{-2}^2 \frac12 \sqrt{4-x^2} \dd{x}$$
Ann
do you at least understand what i've said so far?
also i just realized i missed the bounds on the very first integral in my latex sorry
anyway here is the graph of y=sqrt(4-x^2)
it is a semicircle
the integral of an odd function over a symmetric interval is 0
you know what an odd function is, right?
this is a bit shoddy but it's the first google image search result
can somone help me with my homework??? its about ellipse
determine the standard equation of an ellipse
nothing at all HUHUHUH
co vertices
nope
i have to find the standard form using these
finding the standard equation a hyperbola with given asymptotes and one vertex
im stuck
how do i find b^2 here?
Hi! i was wondering if anyone knew how to solve this?
Just find the intercepts, asymptotes and holes of each function. Then compare it to find what is similar or different.
Thank you!
For example both function has the same y intercept. Np
nani
i rememeber
x/x^2 + c
it literally took me
30 mins to figure out LMAO
ignore pls
f
I think this is true: If I have a ball and I slice the ball with two parallel planes, is it true that both hemispheres had the same volume "cut off" by the planes?
no?
take the unit ball centered at the origin and take z=0.5 and z=-0.1 as your slicing planes
Could some one help me out
what is [[x]] here, floor?
try going through conditions one by one e.g. checking f(sqrt(5)) for all of them to narrow down possibilities
what part of the question are you having trouble with?
So you can just test each function with x = sqrt(5).
- f(sqrt(5)) = 5 so it doesn’t t match
- f(sqrt(5)) = sqrt(5) so it doesn’t match too
- f(sqrt(5)) = 5 - 3 = 2, it match + it s define in R (ez to prove if you need to do that) + but the range isnt Z because the range of x^2 is R, etc… (I let you end the demonstration). So it doesn’t work
- f(sqrt(5)) = [[2.2… ]] = 2 match + domain is R + here the range is Z (we only have integer by taking the floor)
Yeah but why
There has to be a reason
its just notation thats all
you might be able to look up the history of piecewise functions to find out
though there should be a separator like a ; , , , if, for
it's not a bracket in that context
it represents it sorta being split up
into 2 different functions depending on what x is
hi could i get some help on understanding this question? am a bit stuck with the absolutes. I tried to fit in x = -1 and x = 1 but am getting that f(x) = 1 in both cases
no shit