#help-13
428200 messages · Page 493 of 429
2 x 17 = 34 right?
yes
So 5 x 17 is 85 too??????
uh
ok so u take the largest common thing u see in these thingies
which is 17
that's the gcd
What
and
so
for
LCM
u basically
eliminate the similar parts between the two (only keep one)
so 17, right?
Yes
you only keep one of the 17s
Ok
so you get 17 x 2 x 5
o
which is 170
which is the lcm
uh hope that helped lmao
mhm
yes?
bc
85:5 x 17
34: 2 x 17
What
the common thingie is 17
emmm
so you basically
get rid of one of the 17s
because it's repeating
and you multiply the rest together
u take out the repeating part
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gcf i think u mean
.reopen
.reopen
✅
greatest common factor
by multiplying the similar numbers togther in a number set
like
for example
hmmmm
What
uh 72 and 56
72 is 2 x 2 x 2 x 3 x 3
56 is 2 x 2 x 2 x 7
the gcf is 2 x 2 x 2 = 8
What
Can u please add me cuz I need someone to help me when I don't know what to do in math
Im bad at math
I will sned
My brain don't function properly
Jk
Vbbyeeeeeeeeeeeeeeeee
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A flying squirrel jumped from a tree 11 feet in the air at an initial velocity of 9 feet per second. The equation h = -2t^2 + 9t + 11 models his jump where h is height in feet and t is time in seconds
when the did squirrel reach the ground?
can someone work this out theres like 10 of these and i need like a starting point
@ionic slate Has your question been resolved?
What have you tried so far?
ive just substituted 0 for h and tried to factor in order to get two solutions
and pick out the positive
i doubt i am doing it correct tho
d
That is the correct solution
What answer did you get
btw if you can’t factor (although you definitely can factor this one), use the quadratic formula
i got (t+1) and (-2t+11)
wouldnt both of those be negative?
-1 and -5.5?
wait
omfg
i am so stupid
im so sorry
how did i look past that
live and learn folks
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Fireworks are fired from the roof of a 100 foot building and travel 84 feet per second. The equation h = -16t^2 + 84t + 100 models the height h of the fireworks at any given time s seconds
How high did the fireworks get?
How high were the fireworks 2 seconds after they left the roof?
I got the same answer, 204 for these. are they wrong?
204 is correct for the second question but incorrect for the first one.
i mustve messed up badly
on the first one i got -16(169/16) + 84(13/4) + 100
and it came out as 204 idk y
Why did you put the timee as 13/4?
i dont even know i thought i was solving for max
so i used the axis of symmetry
That should give you the correct answerr, what was the formula you used for the axis of symmetryy?
-b/2a
waittt
hold on
somehow i simplified to get 13/4 rather than 21/8
i am way too tired for this LOL
yeaa lmao
just take a breakk lol
tyyyy
npp
its 4 am LOL im tryna cram my hardest
but i endup making the worst mkistakes
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whats the transformation of 2^x+5
@upbeat whale Has your question been resolved?
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Continue the sequence and how
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does this look good?
where does $9 \sqrt{90}$ come?
2022 squared
dont get it why $21 \sqrt{90}=9\sqrt{90}$
2022 squared
There’s a -12sqrt(90)
owh
@left hound Has your question been resolved?
you wrote it as -14sqrt(3)
2022 squared
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Hi ! Can anybody explain these sums to me ,( any one from both sections , I'll try others) it's from the chapter relations and functions.
Third row is incorrect: You want to write -
18(30) +21(V3)(V30) - 12(V3)(V30) - 14(3)
+21(V3)(V30) - 12(V3)(V30) are like terms. 9(V3)(V30)
Sorry, it was closed.
@pallid temple Has your question been resolved?
<@&286206848099549185>
@pallid temple Has your question been resolved?
@pallid temple Has your question been resolved?
,rotate
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why would it equal zero?
for the first equation if x = 0 and y = -10 it would be
0 + -10^2
which is 100
the second would be 3(0) + (-10)
which would be -10
In short,
I plugged in random numbers
have u tried solving algebraically?
I have no idea how to
Here I'll start
and tell me if I get it wrong
y = -3x - 10
x^2 + (-3x-10)^2 = 100
all good so far
and I'm stuck here
dont u do x^2+9x^2+100
@barren hinge Has your question been resolved?
<@&286206848099549185>
<@&286206848099549185>
this is not your channel
that (-3x-10) quantity should be squared, since you're substituting it in for y^2, not just y
and that 10 should be 100
wait what you had it here
the 100 became 10 because I sqiared rooted both sides
that's not how square roots work
oh
if you take the square root of $a^2+b^2=c^2$, you do not get $a+b=c$
a disappointing son
or $a^2+b=c$, as you wrote
a disappointing son
do I do this instead?
i have no idea what that is or where it came from
it's just solving an algebraic equation, now
he multipled the (3x-10)^2 out
i did
nvm he did do it wrong
forgot the formula
how do I solve it algebrcially from there?
you'll end up with a quadratic
Or How do I get rid of the square roots then
solve it as you'd solve any other quadratic
you can't solve a quadratic?
I don't even know what that means
You want me to multiply (-3x-10)^2 through FOIL method?
How is m9/m6=8
not your channel, you've been told multiple times to stick to your own channel
yes
that would be step 1
looks good
so x^2 + 9x^2 + 60x + 100 = 100
exactly
So I was right? or?
no
oh
y = +-10?
how are you getting 10
you need to solve the quadratic first
solve 10x^2+60x=0 first
x = 0
and?
i have no idea
well you have options
you can factor and use the zero product property or you can use the quadratic formula
didn't I just solve it?
you shouldn't be moving 60x over to the other side
if you don't know how to factor and use zero product property, then use quadratic formula
why
because that's not how you solve a quadratic
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Hello
I have a question on this problem
I'm wondering what the form a+bi means
I'm pretty sure I'm supposed to combine coeficients
and simplify like that, but I'm not exactly sure
,w simplify (10+10i)(-5+9i)
@calm bronze nice
there isn't
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np just remember i = sqrt(-1)
this is misleading
Exactly why I came here.
Ik
Btw
This is 2nd option correct
I need some opinions
Some say 2nd and 3rd
I think 2nd but idk
anything times pi is irrational
but idk if t can change that statement
how so?
pi is irrational
ok then, sure
why is what Skid said false?
only rational if they cancel each other
t can be -7pi
So it's 3rd optinon?
is pi + e irrational then?
Hm
pi and (1 - pi) don't cancel each other, but their sum is rational
isnt the answer basically unknowable
i mean cancel each others irrationals
haha yea it's an open problem, I was teasing what Skid said 😛
it is not known whether e + pi is rational, but that doesn't mean it's unknowable
just that no one has found a proof one way or the other
ye
well tru
it can be either
that would be surprising to say the least
Exactly
rational if the irrationals cancel
i would say even astonishing
if t = 7pi -1 it is 1
if you believe hard enough!
same
Skid it can only be one value
no
...
It can only be one operation/value
like a fraction like 1/2
or 35
or 23232.323232
7pi + t is irrational when t = pi and rational when t = -7pi
its irrational
not 92832-397539743 +3232973297 _29372392732
SO its the 3rd answer
Since it can be neither rather both
yes
yes
K
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thx
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Let say, I have to unlock a 3 coded lock in my potion cabinet to get the potion. I remembered the numbers that were used, which is 2,3, and 9, and I know they do not repeat; but unfortunately, I forgot the order of the numbers used to unlock the lock. How many different codes can be used to unlock the cabinet
I know i have to use permutation, so I plug in the permutation formula and got 6
can anybody vouch and double-check for me that it is indeed 6 ways to unlock the code?
Only three possible entries and they're all 2,3,9?
Just in any order?
Yeah, 6 ways.
Well, I assume there's only one way. There's 6 ways to enter the code, 5 of them won't work haha
But yeah we agree here
Ye
thank you, so much
@crimson sedge Has your question been resolved?
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How can I solve this?
The English alphabet has 26 letters, including 5 vowels (A, E, I, O, and U).
How many strings of capital letters are there which contain exactly 3 vowels and 7 consonants, with no repeated letters?
I thought that this was the answer but it is not correct.
10! × (C(5, 3) + C(21, 7))
Here was my thinking: 3 vowels + 7 consonants is 10. You're looking for 3 vowels out of 5 and 7 consenantes out of 21 of them.
My next idea is that this is the correct answer is E out of the options below:
A 10! × (C(5, 3) + C(21, 7)) Incorrect
B 10! − (C(5, 3) × C(21, 7) ) possibly correct
C 21^7× 5^3
D 26^10−21^7−5^3
E C(5, 3) × C(21, 7) ×10! possibly correct
F None are correct
wdym by strings
oh nvm I cant help you sorry
@sacred socket Has your question been resolved?
@sacred socket Has your question been resolved?
@sacred socket Has your question been resolved?
No
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what does the first two lines of part b)'s answer do?
and how can you get it?(just the first two lines of part b 's answer)
@covert raptor Has your question been resolved?
<@&286206848099549185>
What don't you get. They just plugged in U into the pde
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Can someone help me with 1B? I dont understand how the limit is supposed to cancel out
i dont see how that applies here
I think this problem is easily solved by noting cos(npi) = 1 if n is even and cos(npi) = -1 if n is odd
Because once you run to 0
0 * infinity is indeterminate form
and i cant have that
why would i do that 
that doesnt make sense how im allowed to just replace them with 1/n
You know that n goes to infinity
as such you also know that 1/n goes to 0
as its the inverse
Would Squeeze Theorum work on this problem?
No idea what that is
i remember my prof doing something that involved sin using squeeze theorum
this is the key 😶
the sequence is -1, 2, -3, 4, -5, 6, ...
im still lost
i see how u got this
i dont get what ot do with this
that's why the sequence is -1, 2, -3, 4, -5, 6, ...
the sequence that from starting at n=1 going to inf
and plugging in every increment
I'm not sure what you are confused on 😐
uhhh, no?
Thats Squeeze theorum & comparison test thats why i was asking
in b you want to show a sequence diverges, in the one you just sent you show a series converges
oops! I flipped around the words
if comparison test fails doesnt that mean that it doesnt converge
what does comparison test failing mean?
that's too vague for me to understand 😐
Do u know what comparison test is
yes
So when Bn Diverges doesnt that mean An also diverges
Bn being the Sequence i made, An being the Sequence im testing
There are two ways to use comparison
more detail on the comparison?
1/n Diverges
Find an upper bound that converges
but idk how to get it to tht
Then original converges
.
you don't need comparison test for part b
you aren't even trying to show a series diverges
it's a sequence
Im showing if a Sequence Diverges
and I've outlined a solution for you
which it does but i dont get what ur saying
what do you want explained more?
you see how I got this?
yes u plugged in from 1 incrementing up to infinity
1 * cos 1 * pi = -1*1 = -1
2 * cos 2 * pi = 1 * 2 = 2
thats how i assumed u got it
the sequence is ${n(-1)^n}$
yume ♡
using this
So what id Say nCos(npi) = n(-1)^n
yea you can say that
and by alternating series test it diverges?
why do you want to use series tests for everything+?
series tests are theorems about series convergence/divergence
Seeing how it says “sequence”
quite litterally the last few weeks all weve covered is Tests for Series and Sequences
unbounded meaning it goes to Infinity?
kinda
the sequence gets arbitrarily large or arbitrarily small
small meaning negative
that's probably ok
im not understanding this stuff and i got an exam around the courner

hopefully there wont be a problem as complicated as this
this is on the review tho 
i can do A C and D for #1 by myself
but not b
welp, good luck 🙂
just don't spam series tests on every question and you'll be ok 😆
@blissful ibex Has your question been resolved?
ye but i didnt know nay other way to solve it 
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Hey
quick question
the answers say the domain is x < 0
why isnt it x > 0?
(the answer on the book)
Area?
i mean domain
Oh
Try to put x=0.5
x^2 becomes smaller than 0.5
and 2x is larger than x, so larger than x^2
and so you have a negative inside the square root, which cant happen.
Basically you need x^2 - 2x >= 0 for the function to be defined
Solving this inequality gives you x>=2, x < 0
Well it doesn't work on the interval [0, 2) because then either the term under the root is negative or the denominator becomes zero
what would be the difference here between 0.5 and -0.5
Try to put both numbers in the function, see what happens
so 0.5 gives me -3 and -0.5 gives me 2√5
Yeah you can't have a negative inside the square root
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I'm reviewing convexity with some exercises, and this one has me stumped :
Let $I$ be an open interval and $f \in \mathcal{C}^0(I,\bR)$ such that $\forall x\in I, \lim_{h\to 0} \frac{f(x+h)+f(x-h)-2f(x)}{h^2} \ge 0$. Show $f$ is convex. Indication : start with the case where the inequality is strict.
Syst3ms
Now, this is quite easy if f is doubly differentiable
Using the Taylor-Young theorem, one can write $f(x+h) \underset{h \to 0}{=} f(x)+hf'(x)+\frac{h^2}2f''(x)+o(h^2)$, and the expression inside the limit (limitand would be a fun name) cancels out to $f''(x)+o(1)$
Great. But the function in question is only known to be continuous
Following the given indication of using the strict inequality case, I noticed that having a strict inequality means the quantity is strictly positive for small enough h
So for some $\eta > 0$, I have $\forall h\in[-\eta,\eta], \frac{f(x+h)+f(x-h)-2f(x)}{h^2} > 0$
Syst3ms
But I don't really know how to exploit this
Unless some miracle occurs, I'm pretty sure the "barycenter" definition of convexity is a lost cause
Yeah I'm stumped, any help is appreciated
This one is hardcore. I have the full proof in french and it uses an additional lemma
Namely?
It's isn't unlikely that I'd know the result as some edge-of-syllabus thing
Also i'm French
the lemma is : f: I -> R is convex iff for any interval [a;b] in I and for any u in R : the function g(x) = f(x) + u*x is bounded in [a;b]
"et atteint sa borne supérieure en a ou en b" is quite an important hypothesis
otherwise that's true of any continuous function
Yeah but f here is not continuous I think
If it's continuous then the proof is simplified
but the lemma is still not trivial
yeah damn
Wouldn't have figured that out in the amount of time I intended to spend on it
haha this is a hard one. But maybe there is an easier way to do it.
Although if I'm not mistaken I've seen that criterion for convexity elsewhere
gimme a sec
I knew it, it was on one of the exercise sheets of this year
Hah, and that first question was also an exercise on there
lol. sounds like we're supposed to know it
Yep definitely
That lemma was also part of an exercise on our sheet
Except the coefficient µ = -(f(b)-f(a))/(b-a) was given as an indication
Well that hint sounds helpful
Yeah...
Anyway it's kind of jarring because the previous problem I did was significantly easier
It was to show that for all $x, y \in [0,\frac\pi{2}], x < y \implies \frac{x}{y} \le \frac{\sin(x)}{\sin(y)} \le \frac{\pi x}{2y}$
Syst3ms
The second inequality isn't too bad as long as you know a useful sine inequality, the other one is a bit trickier
But nothing like my original question
But I digress
Syst3ms
It's nice to have in mind
haha nice inequality
this is a concavity inequality, but for the trickier of the two demanded inequalities you have to actually use concavity and not just this consequence
But it's high time i closed this
.close
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More tricks? I'm out for now lol.
I'll let you find out
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haha thanks. good luck with that
.close
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I have to get x
I got 24.86
So i wanted to check if i made an error
Cuz it seems unlikely
I don’t this it would be a decimal
So wanted to check
,w sqrt(300) = (1/2) * (x+3) * x * sin(60 deg)
Ok thx soo much
So i will only use the positive value right
Cuz you can’t have negative length
you should solve it yourself tho
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is there any way
i can find the coefficient
if i have (x+a1)(x+a2)...(x+an)
can i find the coefficient
of x^(n-1)
if the leading coefficient is 1 (like it is here), the second coefficient (the one on x^{n-1}) is the sum of the roots
😮
Yes. That's Viete's formulas
so a1+a2+...+an?
All of the coefficients are some symmetric equation of the roots
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hmmm yeah it's technically negative... depends on how you define it
Negative of the roots, but not the negative of whatever was typed above
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Need help with a convergence test question
yes
when n tends towards infinity, can you find an equivalent of the fraction?
(hint : higher powers become far larger than anything of lower degree)
No, I'm struggling with this concept.
Right
I don't sub the value of n = 3 into the "n" variables?
This is a summation
3 is just the starting value
If I write $\sum_{n=3}^{10} x_n$ it's short for $x_3+x_4+\ldots+x_9+x_{10}$
I got that.
When the upper bound is infinity, it's not as simple as saying "sum infinitely many terms" (because nobody actually knows how to do that), but it's a convenient shortcut
Syst3ms
Infinite sums are limits before anything else
Specifically, the limits of the partial sums
So here your task is to use one of the tests you already know to state whether this particular series is convergent or divergent
So converges if p > 1 and diverges if p <equalto 1
yes
well, that's for the specific form 1/n^p
By the way, "<=" is how you would write that second symbol
Thanks.
Say, which tests do you have at your disposal besides p-series (also called Riemann's criterion)?
So, Im at a loss of where to begin the problem.
Ive briefly gone over divergence, integration, geometric
root
ratio
alternating series.
Think that's all of them
@soft cloak
Not even comparison or something of the sort?
Yes, that as well.\
Right, well unfortunately you don't have equivalence, but comparison will do just fine
Although I will use equivalence as a way to find the answer. To prove it, we'll use the tools you have at your disposal
Two sequences are equivalent if their ratio approaches 1. Not too involved.
The "equivalence test" for series is saying that if the positive general terms of two series are equivalent, then the first series if and only if the other one does
So here, we'll use equivalence to reduce this problem to a simple p-series test
Now, we just need the equivalence of rational fractions. Fortunately, it's a theorem that's easy to prove and o remember.
In your case, we have (5n²+3)/(7n^3+20). The idea will be to factor out the highest-degree terms in the numerator and the denominator
5n^2 and 7n^3
Yes, factoring the constants is optional
We get n²(5+3/n²)/(n^3(7+20/n^3)) = 1/n * (5+3/n²)/(7+20/n^3)
But notice that the right-hand factor tends do 5/7 as n tends to infinity
So the general term of your series is equivalent to 5/7n
Now can you say something about the convergence of the series using the p-series test?
No, $5n^2+3 \ne n^2(5+3)$
Syst3ms
You have to factor it all the way
That's as if i said 4*2+1 = 2*(4+1)
Let me format it nicely
$\frac{5n^2+3}{7n^3+20} = \frac{n^2(5+\frac{3}{n^2})}{n^3(7+\frac{20}{n^3})} = \frac{n^2}{n^3}\frac{5+\frac{3}{n^2}}{7+\frac{20}{n^3}} = \frac1{n}\frac{5+\frac{3}{n^2}}{7+\frac{20}{n^3}}$
Syst3ms
Do you follow this ?
Yes
So what we showed is that up to something that tends towards a constant, (5n^2+3)/(7n^3+20) is more or less the same as 1/n
And what can you say about 1/n as far as series are concerned?
for a p-series I'd say it diverges because p is non existent so it is less than zero?
Er.
🥴
n=n^1
so, diverges
yes
the series of 1/n is called the harmonic series, and the fact that it diverges is quite important
why is that?
Its divergence or why it's important?
its importance
It shows that the sum of a sequence that tends towards 0 isn't necessarily finite
But i digress
Ah.
So what the "equivalence test" that you can't actually use tells us is that (5n^2+3)/(7n^3+20) behaves more or less in the same way than 1/n, which diverges
So our series diverges
And here's a general rule
When you have a rational fraction (= a fraction of polynomials), the higher degree terms "win" over the rest
So if you see something complicated like (5n^4+9n^3-πn+1)/(8n^5+42n^3-5), you can know it will behave just like (5n^4)/(8n^5), only keeping the highest degree terms
Intuitively, it's because the higher degree terms grow so much faster than the rest. For example, for very large N, N²+N ≈ N² because N² is way larger
That I'm familiar with from Big O notation
Alternating series?
since everything is positive, you'll have a hard time using alternating series
Although we weren't completely done with the previous example
Rude of me
dw
Because that was with the "equivalence test" which you can't actually use, unfortunately
So instead you'll have to resort to the comparison test
And here the idea is just to use comparisons to only make the highest degree terms appear
You already know it diverges, so if you want to show it with the comparison test, you need to bound it from below with something that diverges
And it will be easiest to bound it from below by something that looks like 1/n
To do that, we'll get rid of these pesky non-highest-degree terms
So now, two questions :
- How can you bound 5n²+n from below to only have a term in n² ?
- How can you bound 7n³+20 from above (it's in the denominator) to only have a term in n³ ?
Well not quite
True
I got that wrong
You can say 5n²+n ≥ 5n² because, well, n ≥ 0
However, you can't say 1/(7n^3+20) ≥ 1/7n^3 because that would mean 7n^3+20 ≤ 7n^3
So you have to bound 20 by something like n^3 (wink wink : n ≥ 3, what is 3^3?)
I'm not following what you mean by bound
@soft cloak Looked at my textbook and some youtube examples. Its not
and 3^3 is 27
<@&286206848099549185> Anyone available?
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I know that sec is the reciprocal of cos but how do you find the others? And how do I use tan < 0?
Please don't occupy multiple help channels.
I know the reciprocal identities, the quotient identities, and the pythagorean identities
Why not use Pythagorean identities?
so like, sin^2 + cos^2 = 1?
So many ways.
There is another Pythagorean identity that helps in doing that.
Then again you already have sin and cos. Doesn't that mean you have tan too already?
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I need help with 4 and 5
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ok my math problem is radical equations and can someone please give me a step by step proccess on doing it . √2x – 5 = x
What's the problem ?
I need help with questions 4 and 5
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Please help me, how do I find the function of this graph
,rotate
i need to write it with absolute values
if this helps, i noticed that the second part equals -2(first part)
first part is x+3, x<-3 second is -2x-6,-3<=x<-2
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please
@azure dock Has your question been resolved?
Why with absolute value signs?
There’s no reason that graph should be like that
this is from a sheet with absolute values, all the other questions had to be like that, so this one has to be like that too probably
i've been trying for 2 hours
Just work out the equations of the lines, it’s a piecewise function with 3 lines
Then the graph of its modulus is shown to the right hand side
This is just 2 points -> eqn of a line
Why?
we had to do it for all the other questions on this sheet so i suppose i need to do it for this one too
Piecewise functions are fine
Are the other questions combinations of multiple lines…?
well :D
But it’s completely unnecessary and it would almost certainly turn out more complicated than the original definition you had
Yeah np
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Hi
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Hello need help with a convergence test question
Root test
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@ripe bison Take the kth root, you get $\frac{2k-3}{4k}$
Sup?
Now take lim as k approaches infinity
@south juniper Im in room 15 now
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hi
going to type out my work real quick, it is a calc honors class and I am trying to find the infliction points
its a simple question really i just need to figure out how to put it into the calculator to find y value
thats the answer to the problem
so the original equation was -x^4 + 24x^2
second derivative was -12x^2 +48 = 0
got x=2
plus or minus 2
and I put it into the table to get the concavity
now I just need to figure out how to get the infliction point
@crimson sedge Has your question been resolved?
<@&286206848099549185>
what's the question??
oh
inflection points are when the second derivative is equal to 0 or undefined (and concavity changes)
how do i get the 80
what do i do on the calculator to make 80 appear
i plug something in somewhere on my calculator to get 80
You plugged in the x value of the inflection point into the original equation to get the y value
understood
let's gooooooooo
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If I'm using Undetermined Coefficients to solve this what is the form of the particular solution?