#help-19
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the shortcut is to count the number of free variables, those are the ones that just belong to R.
the long way is finding a basis
so 4?
i meant those
those tell you the dimensions
the long way might be better if you dont have the intuition for that though
try finding some basis
ok, tysm i'll try this one and send other later
I- The vector w is generated by vectors u and v.
II- Vectors u and v generate the plane x3=0.
III- The vector equation a1u+a2v+a3W= 0 has a unique solution.
IV- The set {u, v} is a base for the plane x3=0.
I, III and IV? #1021175428326633542 #help-0
@lilac seal Has your question been resolved?
whts the q
@lilac seal Has your question been resolved?
@lilac seal Has your question been resolved?
@lilac seal Has your question been resolved?
That tells you the maximum dimension, you still need to determine if the basis vectors are linearly independent or not
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How do I figure out the semi minor axis of an ellipse if I know the semi major axis, both focus points and a point along the ellipse... drawing a line from on focus point to another makes a right angle triangle at the intersection of the elipse. the length of both of does is equal to 2*semimajor axis
$$ b^2 = a^2 (1 - e^2 ) $$
Quantum
$$ where (b) is the semi-minor axis, (a) is the semi-major axis, and (e) is the eccentricity. $$
how did you get eccentricity
Quantum
that is the same formula to get eccentricity , major axis and minor axis
ye but e=
1−(
a
b
)
2
we don't have the semi minor axis
you need semi major and minor to figure out eccentricity right?
if we don't have semi minor how did we get it
at least two values are needed to figure out the left one
tell me what you have ?
I don't have it
bruh
or you mean the question
the question
at coordinantes 1200,0 lies an object the semi major axis is 1484.46m long the first focus point is located at point 0,0 and the second is at -636.35,0 figure out the semi minor axis
the object is at one end of the ellipse
use the formula bor
b2 = a2 - ae2
put the values of b and ae
just show me the soloution im an idiot
Quantum
$$ ae = 636/2 $$
Quantum
not gona argue bro but you said that b is given b you said is the semi minor axis if I recall correctly
yeah b is given , read the question
oh im really dumb I mean to say major axis not minor
1484.46 we are told
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I just taught that few minutes ago to another person lol
so... consider the limit at that point
is each square roughly 1 unit?
then let say I am tracing my function from the left to right, what would my value of that function goes to?
$\lim_{x\rightarrow 2^+} f(x)$ that is
#damiforthepresident
or am I working on the wrong question?
ok. now let's try tracing the function from like 0 and move it to 2. what is your value of your function as you approaching to 2?
I mean, you are not wrong
the limit $x \rightarrow 2^+$ is infinity (you come from the right)
#damiforthepresident
but what about the left one? (you come from the left)
no...
when you come from the right, you go up and up.
but what about from the left to right?
again... start from 0
keep your finger tracing from x = 0 to x = 2
what is your y
close but not quite
yeah, but I am talking about another one
oh
it is -2
I should put your image in full screen
yeah, if it is -2 then you are right
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what have you tried so far
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all good
are you trying to take the limit of the sequence?
yeah
yeah thats not gonna help us here
the problem implies that it converges so
theres no need to use the divergence test
how about lets try splitting fraction up
wym?
its pretty straightforward once you simplify it
y0shi
oh
try that here and see what happens
ok
@old flame Has your question been resolved?
so what do you have after the separation
yeah
I just got the first series
which is 0.02
you have to find common ratio and all that shenanigans
mhm yep
and I see what dami was taking about...
the second one is not gonna be pretty
yeah
I have to use a calculator right?
like ain't no way i'm getting the common ratio without one
well i mean you dont need a calculator to get the common ratio
you need it to get the sum since it wants it to be rounded
y0shi
thats the second one yeah?
yep
see how the common ratio there is just e/5
y0shi
easier to put in the calculator
yep
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i dont understand the questoin
you can just brute force this
so it claims there’s an m such that 17*m ends in 1
right
just consider the multiplication mod 10
how
wait so n and m, they dont end in 5 and an even number?
so n doesn’t end in 5 or an even number
m can be anything?
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You can subtract the top row from the bottom two
Then add the new bottom row to the middle and subtract the new bottom row from the top, should give a nicer matrix
@analog lichen Has your question been resolved?
Log6 = log3+log2
Actually i am afraid of elemantry operators because last time i feelt wrong
I meant operatirs i applied and check in desmos it changed
I would like to know elemantry operations
I meant what row operations is not acceptable
I can multiply any row with scaler and substrcat it?
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When determining the second order derivative of a function: $sin(x^2+y^2)+xyz$ why do we write it as $f''_{xx}$?
Merineth
First order derivative i understand would be $f'_x$
Merineth
Merineth
Isn't this more correct?
We have to indicate it's wrt to some variable because the function contains 3
(considering y and z are also variables)
Merineth
Specifically my question asks for the second order partial derivative of this function
so i have to derive wrt x twice, y twice and z twice?
Does it mention which variable to differentiate with respect to? Also you can write the second order partial like this which imo is pretty clear: $\pdv[2]{f}{x}$
𝓲𝓶𝓣𝔂𝓹𝓞
Merineth
So this would be the first partial derivative wrt x?
$f''_{xx} = 2xcos(x^2+y^2)-4x^2sin(x^2+y^2)$
Merineth
Seems right?
I don't think you put two x's in the subscript
also your first derivative seems right
Merineth
Yeah, I'm pretty sure it's just written $f^{\prime\prime}_{x}$
𝓲𝓶𝓣𝔂𝓹𝓞
No, that's what is unclear to me because the book gives me several answers
Ah, well if your book tells you to do it that way, sure, go with that
$f''{xx},f''{yy},f''{zz},f''{xy},f''{xz},f''{yz}$
Merineth
I just think personally that it's repetitive notation and that this conveys the message "differentiate twice wrt x"
These are all the answers that it says are correct
usually just $f_{xx}$ etc
sobpilled crymaxxer
without the '
Merineth
Couldn't i technically just write this as a gradient the first time?
This would be the partial derivatives wrt x, y and z
creating a gradient
and then i derive each one of those wrt x y and z?
wouldn't this create 3 different gradients out of 1 gradient?
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you end up getting a matrix if you take all of the second derivatives
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if x = 2,32 (32 is repeating)
99.x + 1 = ?
this is what i have done:
232 x 99 = 22968
229,68 + 1 = 230,68
but the answer is just 231 without decimals
what im doing wrong? it must be with repeating numbers
99.x + 1 = ?
where's that coming from
thats the question
2,32 = 2 + 32/99
ok, you'r issue is that $2.32 \redneq 2.\overdot{3}\overdot{2}$
so i find 230,68 but the answer is 231
multiply
ok, your issue is that $2.32 \redneq 2.\dot{3}\dot{2}$
ℝαμΩℕωⅤ
ik but i still cant get the logic behind these repeated numbers
consider the value of 100x
so look
soo
sorry
i didnt understand
i mean
oh
so
100x is 232
then why it's -1
to reach 231
i mean i dont understand
your forgetting the repetition component
yes but i dont know what do with that. how im expected to do operation with a number thats not clear
$2.\overline{32}$ represents $2.323232323232\overline{32}...$
ℝαμΩℕωⅤ
after multiplying by 100, you'll have 232.(still repeating 32s)
100x = 232.323232...
x = 2.323232...
yes
and then subtract the equations
its still 231.32323232
wdym
but the question is 99x, we're doing with 100x. even if i subtract one
it gives me 231.32323232
no
we still got another 1 remaining
so 232.323232 - 2.32323232
100🍎 - 🍎 = 99🍎
should've used ...to imply the repetition but, yeh
that'll give you 99x
so substracting 32323232 from 32323232 will basically be 0
so it's 230
adding 1 gives me 231?
yes
practice
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15
a day is how many hours
25
24
rightt
so if the entire circle is covered in 24 hours
how much of the circle is covered in 1
how do i find that out? Radius is 200 and a revulution is 2π
Do i put arc length as 1?
2pi*radius is the formula for the circumference
but why do i need circumference?
think of it like this
after one day
we have some area
after 1/24 of that day (one hour)
we have a fraction of the entire area
what is that fraction?
1/24?
(we're assuming that the pipe is moving at constant speed)
right
so it's 1/24 of the entire circle's area
what is that
1/24 x πr^2
5235.987
oh i used this reference lol
no not really
connect each side length with the center of the polygon
We draw to middle point of polygon?
right
exactly
you dont have to draw all of it out obviously js draw out one of the 64 triangles youve made
So its a triangle with 2 equal sides and a base of 3
yes
if we split the triangle to two we get the radius right?
Since radius is the line that separates the two triangles
no
hold on lemme make a diagram to show
you see how the line that bisects the triangle isnt actually the whole radius
oh yeah true
however one of two of the green sides are both the radius
its the hypotenusa of the split triangle
we only have one side, so we can't use pythag
two things define a triangle
sidelengths and angles
so do we know anything about the angles?
triangle is 180 degress?
It looks like 30 ° but we arent allowed to guess roght
ye the diagram isn't to scale
it's js to give you an idea of what it looks like
but how many degrees is a full circle?
Wait wouldnt we divide 360 with 64 to find the angle of each section of polygon
Yeah then we just divide the result by 2
mhm
I got 45/16°
now you have a right triangle with an angle and a sidelength
(if you split the triangle down the middle)
so how do we find the radius
Trogonometry, by using sohcahtoa
yep
Wait how did it go again? I use Sin but how i do opposite with angle?
Ok i get this
Sin 45/16 = 1.5/ x
I got 30.57
Thanks bro for help
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What is 2+2
!show
Show your work, and if possible, explain where you are stuck.
Nvm
don't troll please
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do I just step up the integral of 2 to infinity of 1/n(ln(n))^2?
<@&286206848099549185>
<@&286206848099549185>
wait
did u Studied calculus 3
numerical series are from calcu 3
wym?
this exercise is from numerical series exactly calculus 3
ok i give u an example
ok
ok
it has to be an integer though
this the result
i dont have a phone on me right now to show u the steps i took to get this unfortunatelyl
it's all good
good luck
thanks!
@old flame Has your question been resolved?
this kinda helps
i've been looking through it
but it's not exactly what i'm looking for
i'll ask if someone else can help
thank you though!
<@&286206848099549185>
!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
it wants Integral Test
but I really dk how to find the answe
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Hello anyone there
@placid hamlet Has your question been resolved?
no you are the only person on this discord
@placid hamlet Has your question been resolved?
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how do i do the 2nd part?
- Sketch a graph that has a domain of D:{x∈R} and a range of R:{y∈R,y≥2}. Can you draw one that is a function, and one that is not?
Do you remember when something is not a function
@nocturne chasm Has your question been resolved?
Yess this is an easy part of the course. I just don’t know, or maybe I’m just lagging from doing math all day. But, Idk how it can not be a function while fulfilling those reqs
Like nothing that is limited to y=2 and not a function can have a domain of all real numbers
Unless again I’m js not thinking hard enough
Yes, when a vertical line intercepts the curve twice. In other words there are more than one output of y for an input of x.
^ this
I understand that part, thank you :). I’m just unsure of how to draw a graph out that isn’t a function while still having a domain of all real numbers and a range >= 2
you could just draw 2 parallel lines
Wouldn’t that be two functions then?
or just take the function you drew and draw an extra point somewhere
You could say it's one function
How would its equation look like? Or is that not possible
Thank u for your help btw
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I have to calculate this limit
Im not sure what to do next
I could use d'Hopital I think, but that seems like a lot of work
do I have to use d'hopital now?
without the transformation to e^g(x)*lnf(x)?
Isn't this basically the same thing? @sullen ferry
<@&286206848099549185>
whats the ans?
1?
yes
So you've done the most of the things
now transform it to e^gx form
why there's Ln?
f(x)^g(x) = e^g(x) * ln(f(x)), no?
ill send you w8
we write it as this
thats right
we just do some transformation in this
ill try to find the proof for u hold on
np
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(i'm not sure if this is the right place to ask since this is more of a question about the structure of a course than a specific problem)
i'm currently learning ODEs and am mostly just going through a textbook instead of following the lectures since they're pretty low-quality. i noticed that the course goes directly from undetermined coefficients to laplace transforms, but my book has several chapters between them (see photo). is it standard to skip the stuff in chapters 4 and 5 in an ODE class, or should i read them?
No these are not usually skipped
But your course is the ultimate decider. Do whatever you need to for the marks
oh okay, it's a community college class and a lot of the other classes have been pretty poor quality and skipped a lot, so i figured it's good to ask
since im planning on transferring the credit to a 4 year and i dont want to have gaps
ty!
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Can somebody explain why the answer isn't (A)? My understanding is that an inflection point denotes changes in concavity, and the second derivative f''(x) represents concavity where negative numbers mean f(x) is concave down and positive numbers mean f(x) is concave up. I chose (A) because f''(x) = 0 is the point before we go from concave up to down/vice versa. This was marked as wrong and the correct answer is (D), but i'm not sure why.
f'' can also change signs when it has a discontinuity
I heard about that but it says its an inflection point
so doesn't it still have to equal zero
you can have an inflection point and the function not need be differentiable
no not necessarily
are you saying that you can have an inflection point but also not be able to differentiate the function to get the second derivative?
imagine a function where its first derivative looks like this--the sign of the second derivative goes from positive to negative at the point where there is a sharp corner in f', but f'' is never zero
I don't think that function is differentiable
but I think I gave a counterexample
let F(x) = x^2 -- F has a tangent line at x = 0, yet F''(0) = 2
f is differentiable. it isnt smooth but it is differentiable
because that red line is a graph of f', which is well-defined
and continuous
my bad, the graph is for the first derivative, correct
then again im not sold that such function has 2nd derivative
what function would look like that and still be differentiable?
it looks sort of like an abs value graph
inverted
which is continuous but not differentiable
yeah it would probably be some transformation of abs(x) or the step function
but honestly it's not too important the specific function of y in terms of x. moreso its the idea that even if f is continuous, we can have sharp corners on f' representing a change in concavity
i understand now
ty
this picture in particular makes it incredibly intuitive
thanks
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but doesn't this sharp corner make F' not differentiable? thus F'' doesnt exist
f'' doesnt need to exist at the point itself, the condition that i'm using is that for any small epsilon > 0, we have f''(a + epsilon) being a different sign as f''(a - epsilon)
yeah this I agree, okay
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hm, I think I need a hint here
higher!
what have you tried so far
which direction are you working on?
I'm thinking that the contrapositive for the => direction might be easier
so assume there is a nonempty open U in X such that U \cap A is empty
I want to show that the closure of A cannot be all of X now
but I am stuck
alright, then what
hmm
how are open and closed sets related?
they're complements of each other
so I need to show that X\A is open then?
no
$\overline{A} = \bigcap {B \subseteq X : B \supseteq A \text{ and B is closed in X}}$
ah
ah, missing braces but w/e
this is the def of closure I am working with
hm
B is closed* in X?
higher!
Okay so how would you show that the closure of A is not X?
i.e. is a proper subset of X

I just need to find one B such that B is a proper subset of X?
cause then the intersection could never be all of X
I think?
yes!
so you need to find a B such that B contains A and is closed, and is not all of X
you have a U such that U is open and does not contain any of A, and is nonempty

choose B to be the complement of U
yess
then B is a superset of A, a closed subset of X, but smaller than X
ah, clever!
now the other direction...
repost
if every nonempty open subset of X contains a point in A, I need to show that the closure of A is X
hmm
you got this!
.<
let me try for a bit and see what I can come up with
okay, my plan is to show that the only closed subset containing A is X itself
then the closure of A is simply X by default
so I should do this by contradiction
I will assume that there is another closed subset containing A which is not X
alright
now I need to apply my hypotheses in some way
well, if I call this closed subset C, then the complement of C is open and by the hypothesis contains a point of A...
@pastel orbit Has your question been resolved?
@pastel orbit Has your question been resolved?
no, I'm super stuck 
you can do it, I have full faith
I got stuck here, and I'm honestly unsure if this was even a valid way to proceed...
Why wouldn't it be?
Let's say you're proceeding by contrapositive right?
- Assumption: A is not dense
- It follows that there's a C such that A \subseteq C \subsetneq X where C is closed
- ...
- Goal: there exists a nonempty open subset of X not containing a point of A
Fill in the "..."
(Hint: it's entirely analogous to the proof of the other direction)
wait but, I wasn't doing this by contrapositive...

This is one of those theorems where you can actually do both directions at the same time I'm p sure, because you only use iff statements in the proof
But go on, fill in the ... bit

observe that X\C is open because C is closed, and that it's also nonempty because C \subsetneq X. but since A \subseteq C, (X\C) \cap A = empty, so we are done.
I had written down that (X\C) \cap A was empty earlier... but I didn't make anything of it because it didn't give me any tangible contradiction 😭
and that's why contrapositive >> contradiction, folks
I think this works?
yup!
well...
contrapositive only works to prove implications
not statements by themselves
(I am being facetious dw)

I cannot believe I didn't come up with this earlier

note that you can phrase this as a bidirectional proof:
"A is not dense" <=> "there exists closed C containing A but strictly contained in X" <=> "there exists open U not containing A but nonempty"
and then negating both sides gives you the statement
icic
one last thing I want to ask, about the 2nd point
yea
It is just some closed set containing A
It could be the closure, if it's the smallest such set
hm
but if you start from the right and go to the left here, you can't pick C to be the closure
wait nvm that's obvious too
it will just be the complement of U, whatever U is
you're welcome, keep it up
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how would i answer this?
$Pr(4 \leq X \leq 5) = Pr(X=4) + Pr(X=5) = {6 \choose 4} p^4 {(1-p)}^2 , + {6 \choose 5} p^5 {(1-p)}^1 = 15p^4{(1-p)}^2 + 6 p^5 {(1-p)} = (p^4 (1-p)) (15(1-p) + 6p)$
oscoface
@mellow folio Has your question been resolved?
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Hey, just looking for someone to look over my math and correct me on any mistakes I could have made ( math is not a strong suit) thank you.
1 is correct
2 a is correct although I can’t read the process, i think i overdid some steps
2 b is correct
2 c correct
Wooohoo. 4 in a row
You made a mistake in d
The result is correct
But there is a misconception
Sqrt(x) * sqrt(x) is not sqrt(x^2)
Ah I see.
It is (sqrt(x))^2
When you have two things identical multiplying you square the while thing
Because sqrt(x^2) is |x| not x
But sqrtx * sqrtx is x
Ans (sqrt(x))^2 is x
Ohh ok I see what you’re saying.
Yes, the square outside the root
Let me check the others
I dont see the e result
Ok i see now
That one is correct too
Last one is correct
3 a is correct
Now i have to leave
But looks like u got it
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How to check if a real fraction $\frac{p}{q}$ in base m can be precisely represented in base n?\
Is it just checking if $q=n^x$ for any natural number x?
Jigglyproff
do you mean like how 1/2 can be written as 0.5 in base 10 but 1/3 needs a period?
I mean that I can write 3/5 precisely in base 10 but not in base 2
like 0.6 base 10 but 0.5+0.06..... in base 2
0.5+0.06 makes no sense in base 2. you can only use the digits 0 and 1
if they would be in base 2 I mean
0.1 in base 2 is 0.5 in base 10
cant add 0.01 (0.25), cant add 0.001 (0.125) cause they would go above, the next was 0,0001 which is like 0.625 in base 10
therefore I cannot represent 3/5 base 10 in base 2 precisely, because I will never hit that number
I could represent 5/16 in base 2 just fine
see that a number can be written finitely in base b if it can be written as x/b^n
where x is an integer and n is a non-negative integer
but
take the example of b = 2 for example
and p/q = 0.56
my first guess is that it wouldnt work?
we write it in irreducible form 14/25
so given the irreducible form p/q = 14/25
any fractional way to describe this number HAS to be something like (ap)/(aq)
so the denominator has to be divisible by q = 25
but is 2^n ever divisible by 25?
no
so can 14/25 ever be written finitely in base 2?
no
general case:
Prime factors
p/q irreducible fraction
but wouldnt checking if $q=2^n$ is possible with n as integer?
Jigglyproff
check if q can ever divide b^n
meaning
if p_1, p_2,..., p_r are the prime factors of q
oh
they need to be prime factors of b as well
since 2 is prime
the only numbers that can be written finitely in base 2
are something/2^n
so 3/4, 5/8, etc
as soon as the denominator is not a power of 2
(even if not in irreducible form FOR THIS CASE)
it can't be written finitely in base 2
okay lets say we wish to check base 10 -> base 12
3/24 base 10 would not work right
you just happened not to choose the irreducible form, and it works
because irreducible form is 1/8
2 is a factor of 10 and 12
so no problem
0.125 base 10, 0.16 base 12
ah yeah mb its $1/12+6*(12^{-2})$ base 12 -> 0.125 base 10
Jigglyproff
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can someone help me with this
i dont know how to do that
then find the intersection
You dont know that a line is defined like y = mx + b
this is a example
i need someone to do it for me
so i can perpare for my test
my teacher is rude to
No you need to do the exercise yourself so you can understand it
8
answered in the other chat
.close
.close
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Hi I'm not exactly sure where I went wrong here. My teacher's feedback is "There are errors in A, C and D"
@elder canopy Has your question been resolved?
with A, isn't it just taking the integral of p(x) and setting it equal to 30 to get your length?
<@&286206848099549185>
yes it is
so I'm not exactly sure where I went wrong..... was it the integral part?
I dont think so whats the ans given
she didn't give the answer 😭
ty!
I am getting the same ans
Maybe they're being petty because your integration variable is r and not x
or maybe I am wrong too
ok, but that wouldn't make sense for c and d.....
let me check c and d
tbf you very clearly have x there and r as the integration variable
That is fair ground for docking
you mean b? but isn't that the variable they gave for length?
yes, but you need to integrate wrt to x too
not r
or replace the x with r
as it stands e^(-x/10) is a constant wrt the integration
But that's just a theory
wait wait huh? where is this r coming from?
what's this
then what's this
I'd read it as an r
x
you have two scripts for x?
For A, you put x instead of b after integrating and plugging in the bounds, that might’ve been the problem
accident mb
pfft I'm grasping at straws
go tell your teacher if there's no problem
if they're being cryptic on purpose then they don't like you
really? that's so fucked up if that's the case, but I doubt she would take off the entire problem over that....
¯_(ツ)_/¯
you never know
my chem teacher docked 50% marks because I didnt write specific words in the textbook
wait bruh wtf... I replugged part c into the calculator and got 1.68 instead of 2.5 cm.....
wait @fallen hound can I see how you did it? I'm starting to doubt my own work...
in A I did the same thing you did
hmm ok
ughh I hate the way some teachers grade
bc if part A is wrong, then the numbers I used for part C and D is also wrong
so now we can't understand what's wrong w/ A, then the rest of the problem remains a mystery.......
also you didn't add the units in part A
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I have watched videos where they say “suppose there is a polynomial P(x) = some kind of equation” what does P(x) mean ?? Explain it in simple terms as if you are explaining someone with no proper knowledge as I don’t.
its just a name
like when we write random function we say let f(x) = some random function
this sounds like a chatgpt prompt
But yeah
what he said
Ooh ..
argon
It's convenient shorthand to show values of a polynomial
Assuming you don't know what a function is yet, there's a few conditions you need to know before using this notation in general
But for all polynomials it's fine
If we had 2 variables x and y then would we write it as P(x,y)=…?
sure
Thanks!
Is there any resource you know from where I can self study about functions?
Just look up an organic chemistry tutor video
It's a very simple concept to get behind
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what about it
um.
He wants to change it to slope form
He does, i don't think he understands how to solve
!noans
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
enzi²
f(x) is same as y
f(x) = 5x+3
but different notation
google it
f(x) = y, 5 = m (like a multiplier) x = x, + 3 = b
@mystic saffron
a way of writing something
basically
okay
I don't think so he knows what functions are as well
so, remember how we said you can think of f(x) as y?
