#precalculus
1 messages · Page 197 of 1
you have written $\int \frac{1}{3x} dx = \ln(3x) + c$
FlynnXD:
FlynnXD:
if not, you're wrong
Don't mean to disrupt the discussion, I'm just wondering about something. Is this being taught in a precalc class somewhere in the world? The schools I'm familiar only cover this in calc classes.
Ah ok. I wasn't sure if the school system had moved on. Because I have seen way too much calculus in this text channel
^ same
if i have $log_5 6$
Voyager:
No
how does
how does what
$\frac{1}{\frac{log_5 5}{log_5 6}}$
Voyager:
$log_5 6$= $log 6$ / $log 5$ which doesn't equal $log 5$ / $log 6$
Malinky:
OH MY GOD THAT IS SUCH HORRENDOUS LATEX MY EYES ARE LITERALLY BURNING
:) sry am on phone
Voyager:
Voyager:
$\frac{1}{\frac{x}{y}} = \frac{y}{x}$ that's how
Ann:
and $\log_5(5) = 1$
Ann:
$\frac{log_5 5}{log_5 6}$
Voyager:
wait what happens here
$\frac{1}{\frac{x}{y}} = \frac{y}{x}$
Ann:
$\frac{1}{\frac{\log_5(5)}{\log_5(6)}} = \frac{\log_5(6)}{\log_5(5)}$
dude did you type that only after i messaged
Ann:
wtf
and $\log_5(5) = 1$
Malinky:
you're so very welcome.
$\frac{1}{\frac{log_c a}{log_c b}}$
Voyager:
Voyager:
no
$\frac{1}{\frac{\log_c(a)}{\log_c(b)}} = \frac{\log_c(b)}{\log_c(a)} = \log_a(b)$
Ann:
oh alright thanks
how do i start with this
Free Pre-Algebra, Algebra, Trigonometry, Calculus, Geometry, Statistics and Chemistry calculators step-by-step
is this the only way
is it log(x+1) or log(x) + 1?
probably the latter
well that makes stuff a lot easier...
wdym
In this section we solve separable first order differential equations, i.e. differential equations in the form N(y) y' = M(x). We will give a derivation of the solution process to this type of differential equation. We’ll also start looking at finding the interval of val...
You rearrange to write
y dy/dx = -3x² - 4x - 8
Then integrate both sides:
1/2 y² = -x³ - 2x² - 8x
yea thats what i did
Oh yeah don't be like me and forget the +C
ya i did
then the coeffs of x^2 and x are off
Mb I didn't see your work above
y^2=... is really an implicitly defined curve, y isn't a function of x. but if we take sqrt of both sides and "cut" the curve at a specific point, we can make y an explicitly defined function of x
algebra wise yea, just sqrt and pick the "cut" that satisfies y(0)=2
show me your work after y^2/2=...+C
,rotate 45
just to be sure, this means x =0 and y =2 right
yes
sqrt(x) is not x^(-1)
oh its 1/2
that doesn't refute "sqrt(a+b) != sqrt(a)+sqrt(b)"
how does that come into this question, isnt it only sqrt(y)
You're taking the square root of each term individually. That's a no-no
ohh
freshman's dream strikes again, with n=1/2
ty that was the right answer
np
RokettoJanpu:
Compile Error! Click the
reaction for details. (You may edit your message)
Continue from here
,rccw
similar to the last one, this is a separable equation, meaning the x and t stuff can be moved to separate sides and integrated
ive found the value for the constant c
altho im confused because i dont know what x(T) = wants me to enter as my answer
isolate x(t)
i dont have a x(t)
isolate x
RokettoJanpu:
we have the initial condition x(0)=0 so yes plug that in
Does anyone do personal math tutoring
@solemn sluice you probably want to simplify the left side of the equation you are trying to prove so solve for c in terms of a with law of sines
Mmm ok tyvm
Hello I’m from Canada and need help with this log question
How do you multiply exponents with the same base and same power
You just add the powers?
But 6x^2 x 6x^2 = (6x^2)^2 correct?
Yea aka 6^4
Idk what you mean bruh
To answer your original question you just add the powers if they have the same base when multiplying
ie. 5^2 * 5^3 = 3125
2+3 =5
5^5= 3125
$6x^2 \cdot 6x^2 \neq 6^4$
Ann:
@sturdy haven do not use x for multiplication especially when you have a variable called x
@trim fable you good with that question?
So, I dont know why but I am having trouble grasping law of cosines...first off, can when solving a triangle, result to 2 solutions if using the law?
depends on what you're finding
if you're finding an angle from three sides, or a side from the other two and the angle between them, then no, there is never any ambiguity
Nvm, SSA
no, you were right the first time. this is SAS. angle C is opposite side c.
Ah
Sure
yay
So have you added both of them
what is the question again
You’re just adding two quadratic expressions together
you have FOUR equations???
f(x), g(x)
:/
Why 4?
You need 1
Ann wait
i broke it down
Tell us first what you have done first
Oh
ok
h(1)= 1^1 - n(1) +5 h(1) = m(1)^2 + 1 -3 h(-2) = -2^2 -n (-2) +5 h(-2)= m(-2)^2 + -2 +3
= 1 - n +5 = m-2 = 2n+9 = 4m +1
= -n + 6
then I did
this is impossible to read on mobile.
2n+9 = -n +6 4m+1=m-2
n=-1 m=-1
Star, write things down on a piece of paper
LOL idk what i did
what is h(x)?
It’ll be clearer that way
i cant take a pic of it tho
also if you don't know what you did then chances are you did it wrong
thats the problem LOL
Exactly
ik what i did but
Okay let’s start from the beginning
ok
no, write it out explicitly. an explicit formula.
write out what h(x) is explicitly.
let me try brb
Mmh
ok
So what have ya come up with?

have you written out h(x) explicitly?
have you or have you not written out h(x) explicitly?
:C
Star, write it out explicitly
There’s nothing wrong with following the direction we’ve given
ik
i wanted to see if i could do it but ok
ill try
i just didn't
wanna erase lol
Lmao
if you didn't do what you were told to do, say so outright rather than stalling as you just did.
NO!
-n+m+4=0
write out
h(x)
explicitly!
what do u mean
h(x) = (x^2 - nx + 5) + (mx^2 + x - 3) = ???
(m+1)x^2 + (-n+1)x + 2 no bueno????????
bueno?
oh
why couldn't you write this out. why did it take me and abhi so many times.
how did you get that
Try it when you’re more awake
can anyone help with proof by mathematical induction? i got stuck on inductive step... it looks like this: 1 + 2(1/2) + 3(1/2)^2 + 4(1/2)^3 + ... + n(1/2)^n-1 = 4 - ((n+2) / (2^n-1))
first you assume that n=k
and then i got stuck on n=k+1
<@&286206848099549185>
generally $\int_a^b |f(x)| \dd{x} \neq \absv{\int_a^b f(x) \dd{x}}$
Ann:
oh
so how can i use abs(x^2-x) ?
i mean integrate it*
is there any methode for the absolute value ?
i mean you tried splitting the integral up based on the sign of x^2 - x
which is good
you just didn't do it properly
x^2 - x is less than zero iff x ∈ ]0,1[
so you'd be splitting this up as $\int_{-1}^0 + \int_0^1 + \int_1^2$
Ann:
@harsh cipher yup
ok thanks
@fluid shore hi 😛
oh no
i wanted to ask u that before
I realized what i was doing wrong
but i dont understand what im supposed to do
i have a test tom im stressed :c
so what i was doing was
h(x)= f(x) + g(x) and i subbed in 1 into the equation and solved but then
instead u add them like uh.. in a way idk how to
@fluid shore
like how would u add ( x^2 -nx + 5 ) + (mx^2 + x -3 )
coz what i was doing before was just subbing in 1 for x and solving that^^
but u add them first? its kinda confusing coz
idk how she got that yesterday and i was too tired too finish
Well, can you see that x^2 and mx^2 have a common factor of x^2?
Abhijeet Vats:
hmm
why +1?
uh
oh..
nvm
u factored the x^2
hmm ok makes sense
waitttt
😦
why is it
m-n=-1???
im getting m-n
@fluid shore 😦
:///
Uh wait can you post the question again?
Sorry btw, i’m in camp so i’ll have to come and go as things get busy
@trim fable
Like, post the entire question
It's just a letter after all
A variable
I think it's safe to assume that's a function d in terms of t
Okay so
😛
$f(x) + g(x) = h(x) = (x^2-nx+5) + (mx^2 + x -3) = (m+1)x^2 + (1-n)x +2$
Abhijeet Vats:
^Do you understand what i've written above?
yeah
Okay so
5-3 is what?
$h(x) = (m+1)x^2 + (1-n)x + 2$
Abhijeet Vats:
No forget about what you've gotten before
oh
What you have now is what matters
^Good life lesson tbh
So, you have been told that (1,3) and (-2,18) satisfy h(x)
What does it mean for those points to satisfy h(x)?
Nope, it is significant
What does it mean for those points to satisfy h(x)
U MAKE THE EQUATION EQUAL TO ITTTTTTTTTTTTTT
Indeed
So h(1) = 3 and h(-2) = 18
oh just to clarify coz i think i forgot
Then, you'll get two equations in two unknown variables m & n
yeah
ok ikwhat to do now 😄
tho like question about it
u know how i was adding before
whats the difference between adding it the way u showed me or just
subbing things right away and then solving
Like, you don't know if they satisfy f(x) and g(x) individually. You can't say that f(1) = 3. You can say that f(1) + g(1) = 3
OHH
Yeap, you substitute x = 1 into it
ok
so u always say that
like for the next one
18= f(-2) + g(-2)
right
so i should start off a question by stating something like that
3= ( 1)^2 -n(1) + 5) + (m(1)^2 +1-3)
3= 1 -n +5 +m -2
3=-n+m+4
-1=n+m
Uh no
oh so what i did before was right I was just not making it equal to y
yeah ik i wanted to see
You should start off the question by finding h(x) explicitly
if i got the answer thhat way
and it worked out
whys that?
is that process considered wrong
idk for me i feel like it really simplifies things a lot, i do get ur way buut its kinda complicated
Well, there is a common consensus that working in variables does allow you to generalize things easily
yeah
That is, suppose I give you two other pairs of numbers that, supposedly, satisfy h(x) = f(x)+g(x)
If you didn't have h(x) written down explicitly, you'd have to do the entire calculation again
oh
But if you did have it written down explicitly, it'd be way easier for you to get to the end
what do u mean by explicitly
For this specific problem, it's not a big issue. For other problems, it can be an issue
Like, a formula for h(x)
Like the one that I showed you a while ago
oh
Also, question's
?
yeah
LOL
hey also
determining the domain and range for
composite functions confuse me a bit and
like can we do this together
so for fog u compare inner to outer right
so the range of g(x) and make that the domain of f(x)
but like its really confusing 😦
i do get it at times but then i just blank out
like we use graphs to do it
I have two functions that are defined as follows:
$f:\bR \rightarrow \bR$ and $g: \bR \rightarrow \bR$
Abhijeet Vats:
yeah
That's what your functions are
Yes
ok
You can use any real number. The functions are defined for all reals
ok so for fog
see the pink line is the range of g(x) and I made it the domain of f(x)
but why is the domain for the composite gonna be XER ?
also how would u find the range
Uh have you done the necessary reading on range and domain?
what do u mean
for each ye so
for the first one Second one
Domain: x is an element of the reals x is an element of the reals
Range: Y>=0, y is an element of the reals y is an element of the reals
OH BTW YAY I GOT THE ANSWERR!! n=3, m=2 🙂
thanks for that help lol
Well, all you need to do is to see that f(g(x)) = x^2-8
So, that's defined for every real number x
So that would be your domain
Well, it would though? I mean, I haven't encountered cases where that doesn't really work out
To determine what the domain is, you just need to determine when that function is defined and when it isn't
oh
and what do u mean by that
like if its valid? the points
thats what my teacher says
So, for example, y = 1/x is defined for all real numbers aside from when x = 0
So its domain is given by $\bR-{0}$
Abhijeet Vats:
let me show u one from my notes and try to do it algebraically
Sure
Uh $f(x) = \frac{1}{x}$ and $g(x) = \frac{1}{x^2-1}$
Abhijeet Vats:
ok
Okay so f(x) is clearly undefined at x = 0. g(x) is undefined at x = 1 and x = -1
yes
wow..
so u can just do that
😮
my teacher drew it out
ill try to draw it to show u?
or do u get what i mean
Indeed, that's correct
However, keep in mind that the domain of f(g(x)) does not include x = 1 and x = -1.
Because computing f(g(x)) at x = 1 or x = -1 involves computing g(1) and g(-1), both of which are clearly undefined
No
Yea division by 0 is undefined
Well, it does though
oh
We did it without drawing any graphs
We determined the domain without using graphs. The domain is the set of real numbers that don't include 1 and -1
Wel, try it
I can't be doing everything for you, right?
yeah
ik but this is really helping
oh and these qre questions from the notes tho
that our teacher did with us soooo
i already have the answers for that 😛
i just wanted to see if i could do it an easier way than graphs..
OHH
one more thing
@fluid shore So I have a question about these
Ok so like i get the dividing one coz the first one has a lot of asymptotes so it would be
log2x/sinx
and the third one has multiple zeros so it means it would be
sinx/log2x
then the 4th graph (second row first one) has horizontal asymptotes and zeros
so would it be multiplication so (log2x)*(sinx)
@fluid shore
sorry for the ping if it annoys u
also addition would be the same either way so
(log2x) + (sinx)
1+0 =1 so end behaviour is positive
Subtraction
(log2x)-(sinx)
1-0=1 end behaviour is positive
(sinx)-(log2x)
0-1 end behaviour is negative
so then the last graph would be (sinx)-(log2x) ?
I mean, I'm sort of not sitting down with a pen and paper
So i can't just verify what your answers are
I mean, just graph them out on desmos and see if you're correct lol
ohhhhhhhhhhhhhhhhhhhhhhhhhhhh
true true
but my question LOL
was how to determine the last two
these ones
(log2x) + (sinx)
1+0 =1 so end behaviour is positive
Subtraction
(log2x)-(sinx)
1-0=1 end behaviour is positive
unless someone else can help since ur busy and thats fine 😛
thanks soo much thoooooo 😄
what is the domain of $\sqrt{x+1} - 2\log(-(x+1))$?
Ann:
what?
hi Ann
i don't understand your question
at pi why do we move down 1 square which is equal to 0.25
I think we have to move down 4 squares
why
cos pi = (-1,0)
can we cut the pointless filler convo that i'm absolutely not up for sustaining right now and you tell me whether or not what i said made it clearer how to proceed on your problem
why oof..
yes i was
do you know how to find the domain of a function defined by a formula
go look this shit up or something
oh um
ok
also
i had a question about this
first one would be log2x / sinx right?
there's nothing else it could be
then third one would be sinx/log2x
and then the fourth would be (sinx)(log2x)
then the last one is sinx-log2x right?
but then idk how to determine the last two
but im left with sinx+log2x and log2x-sinx
so then how would i determine those
gee i don't fucking know
the fifth and sixth graphs look like mirror images of one another so maybe they are log - sin and sin - log
oh i got it
middle top is
log2x+sin
tho is it coz the start of it goes up
see that part of it
and second is sinx-log2x
@willow bear
x(t) = 2cos^2t - 2sin^2t
y(t) = 4 - [cos(2t)]^2
how do i solve this
using tri identities
wdym solve
double angle formula for cos
that gets me 4 - (cos^2t - sin^2t)^2 and idk what to do from there
look at what you have in brackets and then look at x(t)
er
OH
hm
but x(t) is multiplied by 2 thougfh
the cos2t
ohh
i think i can see
x(t)/2 = cos^2t - sin^2t
then i can plug in for x(t)/2
k thx
np
i feel dumb now lol
aha
its a parabola
except @native sequoia how do you know where it's restricted
the domain and range
and t also
I'd say assume t is over the reals, and we know x(t)=2cos(2t), so...
errrr what?
what values does x(t) go over?
nah, think about the range of cos
why is it graphed sideways on desmos?
im confused
i thought cos was horizontal
remember when math used to be easy....
can you screenshot what you see on desmos
looks like desmos is letting the vertical axis be the t-axis for some godforsaken reason
oh
it's because of the x probably
there we go
wait so shouldn't x be infinite
goddamn alg 2 & below was so much easier
for t over the reals, 2cos(2t) has range -2 to 2
i.e. x(t) goes over the values between -2 to 2
huh
what
i thought the domain is infinite for sin and cos
and range is limited to whatever
or are we talking about the unit circle
i think i should just get some sleep
eh whatever i'll figure it out in class tmrw
it's getting late
well at least comp sci is easy lmao
How can I solve
Jason_Bjorn:
symbolab says to use Newton Raphson, which has not been taught in my class, so I don't think we use that
and WA doesn't show any actual steps
What have you tried?
f o g(x) = f(g(x))
For 1, we’d have: f(g(x))= x^2 - 8
Are there any restrictions on the domain?
No. We can input any real number
Now, for the range, we’re looking for values of x which output.
Looking at the function, we notice that x^2 is positive for all x
So, the minimum output of x^2 is 0.
Thus, the range, at the smallest, is -8.
And all numbers greater than -8 can be given.
So the range is all numbers >= -8
So the range is all numbers >= -8
are you insistent on avoiding interval notation or sth
what stopped you from saying [-8, +∞)
Didn’t think he’d understand that
On my test there was this question... "There are 2 letters that dis include x and y, then 3 numbers from 0-9, the first of which cannot be be 0, and then any two letters but they can not be repeated."
So I did
24×24×9×10×10×26×25
Not sure if that is right
<@&286206848099549185>
Also not sure if I should use this ^
Ping helpers after 15minutes, not before.
Yes
Hmmm... interesting.
What?
@patent beacon I’m wondering the same thing
what does 'dis' include mean?
Like is the answer a number?
oh, exclude right
I'm guessing they're looking for letter letter number number number letter letter ?
perms for that
Oh
So questions pretty much have to include "What is..."
disinclude 
That makes sense i think
Where's your "what is..."?
I would guess number of perms for a 7 blank long code with the given rules
Are you here @stark trench ?
@tiny verge yep
Also the question is based off my memory
Not the exact thing
But the numbers are the same
Also I meant disinclude
But autocorrect gives it a space...
Essentially, it wanted us to use fundamental counting theory
With 7 spots
Are you asking "how many ways to make this string"?
The first 2 were any letters that disincluded X and Y
hm, so 7 spots with allowing repeated numbers, not allowing repeated letters on the last 2 spots, and allowing repeated letters on the 1st two spots where you can't have x and y, yes?
At the end it says
I think you've got it right, then
"The last 2 spots can be used for any letter, but these letters cannot be repeated"
I'm not sure if that refers to all previous letters
Or just from that point
So I was like...
hm, my thought exactly
Do I use 22x21
Or 26x25
Idk tho
Anyways, fuck that test.
I looked back at my answers in my head.
And I got like 7-8 mc /26
Rip
Can someone explain this?
what's confusing you about this
I don't understand the calculation where does it come from
it's not a calculation
So how do you get it?
...you don't
well i mean
ok
you CAN sort of do some pseudo-algebraic manipulation here
like you can start from $\frac{f(x+h) - f(x)}{h} \approx f'(x)$
Ann:
multiply through by h and add f(x) to both sides and you'll get what your paper says
Oh OK I understand I read it like
f '(x+h) ~ f(x) + f '(x) h
so you inserted an extra apostrophe in there is what you're saying
...sometimes this form can be useful?
With the basic formula you try to reach f(x+h)?
Thats the question
I think I get it now thanks for the help
coefficient of x^4 in the expansion (2x+1)(x-3)^6. how do you solve this again?
How to solve x=5arctan(x)?
Cannot
I mean, you can, but it's not exactly straightforward precalc
Cannot algebraically
You can approximate solutions with many methods, up to you if you're for that
I got something like this:
x = 5*arctan(x)
x/5 = arctan(x)
x = tan(x/5) => what values of x make this true?
keeping in mind of course that tan(x)=sin(x)/cos(x)
@patent beacon tangent is periodic though
hrm... the 5 throws a wrench into it
I see your point
Ok. thanks @patent beacon
if i have this function with like 2 turning points but only one point cross the x axis how do i figure out the function
sure
yea
what
the function isnt given
it is a polynomial
here are the points where it crosses
the turning point
you are given like a point
can you show
the stuff in the picture is all your given
yea
i dont think thats the problem
but okay
can you show the problem
you are given?
from the textbook or whatever
idk what a degree is
highest power
yea
yea
ok
from the graph
that 27
ok
can you keep going?
keep plugging in points
and doing system of equations?
and also by knowing that at turning points
f' is 0?
no
okay
f(x) = ax^3+bx^2+cx+27
f'(x) = 3ax^2+2bx+c
f'(3.523) = 0
f'(-0.189) = 0
f(2.097) = 0
ok
those are your 3 equations
for your 3 constants ig
can you solve them?
do you know how i got those equations
i know how you got 2
what 2
but the one with the 2. 097 wouln't be zero
cuz its not like a turning point, the top two are
write out the equations
and solve for your constants
unfold your definition
you know f(x)
i can try
ok i cant do it
what did yo utry
oh wait
i think i got it
i assum i set them all qual to each other then solve for a b and c right?
you can do that ig
f'(3.523)=f'(-0.189)=f(2.097)=0
its just a system of equations
sure
is b^x = 1/b^-x?
yes
I can't seem to figure out part A of this problem. Can anyone help? (please ping me if you do so I can make sure I see it)
I got an answer (about 38.838 mi) very close to the real answer (about 38.65 mi) by assuming that KROK was broadcasting at a 50 degree angle to the east as well but I don't know if I could assume that or, if I could, why that makes sense.
yea ok ill explain how to get the angle
i assum from there you can do the work
There is another angle so now you should be able to calculate all the angles
@runic cradle
(y-2)^2=4(x+3)
Why is the focus of this parabola (-2,2)
I thought the focus is (h+p,k)
And p is equal to 1
With what
question
at pi/2 or 2pi/4 why is the y-coordinate 0.75?
equation given for the above answer was y= cos(x- pi/4)
I just couldn't get that point when trying to graph
it's not supposed to be 0.75, the graph is honestly a bit poor
it looks like they approximated the sinusoid by stitching together pieces of a parabola
well its 0.707 or something to be exact...
no
it's 1/sqrt(2)
anyway yeah this isn't a good graph. i can see the seams. it's not clean at all.
okay. why the y coord is at where it is when x = 0?
same reason. it's supposed to be 1/sqrt(2) too.