#help-42
1 messages · Page 72 of 1
Not quite no, you can restrict delta to be less than whatever [positive] number you want whenever you want
The fact that you had a fraction last time is irrelevant (also that argument I find a bit sus too but another time
)
ah ok, cause you are just setting the distance for delta... like as long as you can find the sorresponding eps and eps+f(a), eps-f(a) you are good
so as long as delta is positive
and bigger than 0
i think you can set delta to be 0 too, if its just a point, but not sure how that helps with continuity
nah now I gotta know
ok yea
yayy
working on this one now, Im thinking to prove by contradiction, negate the continuity def, use triangle inequality (negative one) when dealing w inequalities and hopefully find smth that contradicts?
Yep, you can set your delta to be whatever you want and that makes your life easiest
And cool
happy with that, there's an implicit intermediate step where you use the triangle inequality I see 
And for this, it should be much easier and can be done directly... 
yea I think I can just say that ||f(x)| - |f(a)| | <=.... and then directly just say its continuous
like ofc I had all the rest of the continuity definition
I crossed out the part where I was trying to do contradiction
hm maybe I should rewrite?
ok i’ll be back in 30min-1hr
Yep, reverse triangle inequality is all you need 
And you should 
@glad sinew Has your question been resolved?
okiee
i just realized for converse if |x-a| |is equal to | |x| -|a|| then the delta doesn’t hold
but there still exists a delta where it could be the case that:
| |x|-|a| | < delta < |x-a|
for the converse
for this question I dont get how max and min of a function affects the function's continuity if you already know that f and g are continous
<@&286206848099549185>
why is f increasing a reason for it to be bounded by f(a)?
<@&286206848099549185>
i dont get it :((
I get the part about a-1 <= x < a
right
but you are saying f is continous at a, so theres also x bigger than a
right? as long as the x is within (delta - a, delta+a)
<@&286206848099549185>
Can you send the entire proof
hey i’m actually gonna sleep now
i took screenshots of my question
i’ll ask again tmr
thank you tho
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can someone help me with this:
solve for the Fourier Series in Trigonometric and Exponential Form
@radiant notch Has your question been resolved?
<@&286206848099549185>
what have you tried?
@radiant notch Has your question been resolved?
nothing i dont understand about it lmao
probably you have some formulas you could start with?
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@mossy cliff Has your question been resolved?
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can someone help me with b and d
Do you have formulas
What have you tried then
You’re applying 1% compound interest 12 times every month for 6 months?
i dont believe so
im applying 1% compiund interest onto 5000 every month for 6 years
oh
im just trying to find the balance after 6 years of 1% per month
but not sure how to do that
Ah
So ignore the n value
Cause that’ll always be 1
Now find how many months in 6 years
72
ah i see
Another thing
The equation is
P(1+r/n)^nt
So your original one was missing the final n in the exponent too
whats n standing for?
i see
so id onyl do this if the question were asking how much interest is he gaining per month or something
No
without the ^72?
For that you would find how much he has after a month and subtract how much he had the previous month
oh i see
Phhh wait
Did you divide by 12 because you wanted to find the percent per month?
yes
but i jsut read the question again and it asks for the balance
Yeah one period is already a month, so that’s not needed
so this is right
Yes
No problem
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$\int_0^3\left[x^2\right]+\left[\frac{x^2}{2}\right]dx$
ƒ(Why am. I here)=I don't know
other than breaking this into multiple intervals
is there an way too solve it
for instance
$\int_0^n\left[x\right]dx=\frac{n\left(n-1\right)}{2}$
ƒ(Why am. I here)=I don't know
ƒ(Why am. I here)=I don't know
I don't think there is a similar closed form
For instance consider [x^2] upto 1, it's 0
Similarly the integral to 2 is
0+sqrt2-1)+ something
Which suggests a neat closed form doesn't exist
Am I right?
,w integral from 0 to n of floor (x^2)
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<@&286206848099549185>
break the integral
at integral
values
and then add
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its simple but i cant seem to understand
drawing a venn diagram might help
it isnt really specified if theyre disjoint or not so i am confused
you'll get the same result regardless
you can draw two diagrams if you want to consider both cases
alright ill try
but are you sure any property or law wont apply here?
like maybe we can use DeMorgans law somehow?
if you can rewrite X-Y in a form that allows you to invoke de morgan, you can certainly use it
Someone prove that ô1 is 2*angle m1
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Result:
5
like like
i dont get how euler totient function works here
i just followed blindly
nd got remainder to be 5
also but i made an assumptio
that after 6 sets remainder remain same
wait
i did not understand this part
Okay
So there’s a theorem in number theory that says a^phi(n) is congruent to 1 mod n
When a and n are relatively prime
euler totient
This is Euler’s theorem, and it’s not awful to prove at all in a reduced residue system
i did get that
but i dont understand this last part
nope
but ik we predict prime numbers with it? ig
Okay so
Are yoy familiar with modular arithmetic
We may have to do some background building
a lil
i did not touchhed upon NT much
we usually do remainder ques with binomial thm
Okay
Well basically modular arithmetic is how you get here
So did you understand all lol the previous steps
Or no
i kinda swallowed the concept of euler totient function
i just dont know why we using it
usually i used the function to calculate number of positive integers less than or equal to n nd coprime to it
So a little bit of background building g
We say b is a inverse of a mod n if ab = 1 mod n
example
ohh the negative remainder thingy
Ok
So I’m going to make a claim here that I’m not going g to justify bc it would take forever
If a is relatively prime to n, then a has a multiplicative inverse mod n
Reasonable?
so thats the reasoning to using ET funcn
oh a lil
i'll do a research myself after
i get after
but the last line
why more than 4
nd it stays 41 mod 46
will in case of 5
it will stay same after tower of 6
Okay s
Well can those 4 and 5 cases really exist?
Okay
So the thing is
We KNOW that x3 is 3 mod 4
Therefore, we can compute what x2 is going to be
And what x is going to be
Right?
here
It’s always going to be 3 mod r
Because 3^k is always 3 mod 4
For odd k
This is only true when we go 4 or more steps up though
Because we need to get to x3 first
So we need x0, x1, x2, x3 to all exist
so in my question
can we say 6 steps
since it comes like that at 6
i followed that
i got 5 to be the remainder
Ok so your issue here is that 5 and 24*5 aren’t relatively prime
So Euler’s theorem doesn’t work
lol
Well what you need to do is divide out 5 from the modular congruence
So you get 5^( (5^5^5^5…)-1))
Let x0 be this mod 24
Let x1 = 5^5^5^5…-1 mod phi(24)
And keep going

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Can someone check whether its correct or not? 😭
You can plot the function you get on desmos.com/graphing
uhh
Plotting is a good way to check your answer
Ohh
Ohh kk
yea thats whats wrong
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We have a,b,c are real numbers, a,b,c>=0 and a+b+c=3
Find the minimum value of P = 1/(a+1) + 1/(ab+1) +1/(abc+3)
Sorry I dont know how to use latex
I am a bit confused about how you are meant to compare Taylor approximations together. Consider a function $\6fx$, which is analytic on its domain, with two taylor series representations, $\6{T_c}x$ and $\6{T_k}x$ each centered around some points $c$ and $k$. Now, with the functions being analytic, it follows that $\6fx = \6{T_c}x = \6{T_k}x$. But if you are looking to make some approximation of the function $f$ via its Taylor series of order $n$, then it is not generally true that [
\6{T_c^2}x = \6{T_k^2}x
]
So my question becomes how exactly do taylor approximations with different centres compare with each other? What exactly is the error that makes us not able to have the series be equal to each other?
We have a,b,c are real numbers, a,b,c>=0 and a+b+c=3
Find the minimum value of P = 1/(a+1) + 1/(ab+1) +1/(abc+3)
Sorry I dont know how to use latex
can anyone guide me through the steps to match the equation of a slope field. This one is either xy, x, x - y, or x + y
the one that I am confident to rule out myself is the x
I also notice that the slopes are positive all in first quadrant and negative all in third quadrant
and that slope is 0 in the middle there
help channels r broken
open a forum thread in #1021175428326633542
Ohh okay thank you!!
I have a question to find the sum of the first 9 terms of the series 6+0.6^26+0.6^3+60.6^46+... Can u please check if im correct: I got that r = (0.6^36)/(0.6^2*6)=3/5 the S9=(6(1-3/5^9))/1-3/5 = 14.85
Hi guys, can somebody please help me understand what are F^S and R^[0,1]? I get that for example R^2 is the set of all the ordered pairs of real numbers and if I understood correctly it denotes the set of functions that sends each pair (a,b) where a,b are in R to a number in R. Basically, every point on the plane is sent to a number on the real line.
i have a question
Jack is reading a book. If on the first day he reads 3|7 of the pages of the book and on the second day he reads 3|10 of the remaining ones, calculate how many pages there are in the book knowing that there are still 80 pages left to read. can someone help me??
So what fraction of the book is left?
4/7
so?
(btw he reads 3/10 of the remaining pages)
So 4/7 isn't correct
3/10 of 4/7
Yeah, you're nearly there
So what fraction of the remaining pages does he not read?
19/70
4/7-3/10 ??
Stop guessing
Okay, so John can either read the remaining pages, or not read the remaining pages
So what do these two fractions have to add up to?
Given that they are the only two options
3/10 and 3/7
Ignore the 3/7 here for now
Cause we're talking about a fraction of 3/7
we have to add 3/10
Okay, so these two parts have to add up to 1 - 3/7 = 4/7
So 3/10 * 4/7 + 7/10 * 4/7 = 4/7
Or just 1 - 3/10 is 7/10
That's what I was looking for
7/10
So he hasn't read 7/10 of the remaining pages, or 7/10 * 4/7 in total
Yeah so it's just 7/10 * 4/7 * x = 80
28/70 *x =80
south
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How do i do this?
See which one violates properties of an equivalence relation
yes i tried that but im not sure how to do it without being given two sets
!show
Show your work, and if possible, explain where you are stuck.
what do you mean "given two sets"?
I found its reflexive given k=1
What is "its"?
R
sounds good so far.
For S when k=0 its reflexive
Assume xRy is true, does this imply that yRx is true too?
Can you provide an example?
For 1/k
Or, prove why yes?
But is 1/k always an integer?
Oh no it is not
So it is not true
because if x=1 and y=2 it works
but for y=2 and x=1 it does not
And the relation S is reflexive
Because for x=1 and y=2 it works for k=1
and for x=2 and y=1 it works for k=-1
exactly right
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how do u do this question
start from f'', make a function that satisfies the conditions for that
then you can integrate and solve for the two unknown constants using the rest of the info
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help with understanding this proof
@lunar token Has your question been resolved?
@lunar token Has your question been resolved?
the idea is that every domino on a checkerboard takes up a black and white square, so when you have a board with more white squares than black squares, it can't be done
because anything with dominos will cover an equal number of black and white squares
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Given a 5 6 Matrix, in how many ways can we move from cell 1 1 to 5 6, if we are allowed to move right or down and we can only change directions three times
I tried 9!/(4!5!) which is 126 but I'm not sure how to check for the cases where it changes directions more than 3 times
The correct answer is 33
You can stars and bars the moves
id break it into two cases, since the direction change amount is odd, if we start with an UP, our ending move must be a RIGHT
A star being "move forward"
And a bar being "turn"
Ah, but that doesn't count for less than 3 turns
Or it doesn't count for leaving the matrix
it is definitely some form of stars and bars
@void pendant Has your question been resolved?
@void pendant what do you need help with?
u probably dont need cases, its a multiplication of two binomial coefficients
stars and bars on two things, the UP's being distributed into 2 blocks, and RIGHT's being distributed into 2 blocks
How many stars and bars?
5 stars and 4 bars?
Thats for 3 changes of direction,right?
yeah
I did xD yJ (5-x)D (4-y)J where x<5 and y<4
Sorry for notation but d is right and j is down
For x there are 4 cases multiplied by 3. And then I do the same when starting with a down
nvm I think I got it
thanks
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Hi, the Picture on the left is the question, the right is my work so far. I’m not really sure what to do next, and I also don’t know how these planes are represented visually.
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HIIIIII
hi well, for now no
cause its annoying to open, close, reopen channels for each question
so?
I usually have alot of questions as I work through the problems
then open the channel as you go
theres open channels tho
it is not that deep
please only open help channel if you have one question
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express as a product: 1-cot(a)
@amber roost
Basically you know
$cotx = \frac{cosx}{sinx}$
Put every term on sinx
Tittom_123
So 1 become sinx/sinx
alr
1-cot(a)
Csc(a)(sin(a)-cos(a))
cos(a)(sec(a)-csc(a))
these are the 2 forms i got
but i cant express them as a product
the csc one is the right one, because it's a product
lol but u cant use subtraction
They are both products
for 1+tan(a)
1+tan(a)
sec(a)(cos(a)+sin(a))
Sin(a)+cos(a)
Sqrt(2)(1/sqrt(2) * sin(a) + 1/sqrt(2) * cos(a))
Sqrt(2)(cos pi/4 * sin(a) + sin pi/4*cos(a))
Sqrt(2)(sin(a)cos(pi/4)+cos(a)sin(pi/4))
Sqrt(2)*sin(a+pi/4)
sec(a)*sqrt(2)*sin(a+pi/4)
You can't simplify without the -
the bottom equation is how u want it
Where did the secx went?
sec(a)
Yes
And why √(2) ?
i took it out of sin(a)+cos(a)
How?
No, I mean from where does it appears
i just factored it out
Oh
yeah its a weird question
This doesn't work because
$\frac{1}{\sqrt{2}} \neq cos(\frac{\pi}{4})$
Tittom_123
yes it does
1/sqrt(2) = sqrt(2)/2
cos(pi/4) = sqrt(2)/2
45-45-90 triangle rules
@amber roost
You are better of working with 1/2
Like this@nimble urchin
Since
$cosxcosy = \frac{1}{2}\left(sin\left(x-y\right) + cos\left(x+y\right)\right)$
$sinxsiny = \frac{1}{2}\left(sin\left(x-y\right) - cos\left(x+y\right)\right)$
Tittom_123
@nimble urchin Has your question been resolved?
Oh, yeah, mbd lol
@nimble urchin Has your question been resolved?
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Didn't you had an other problem or nah?
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@amber roost
$\sqrt{2} = sec(\frac{\pi}{4})$
Tittom_123
Or sec45°
$\frac{cos45}{cos10}\left(tan30 + cos180\right)$
I will let you work from this now
Tittom_123
? what
What?
what is that expression
This with trig
that is just extremely wrong
Let me help my student, all the help I gave him yet gave him the right answers@quaint sphinx
It isn't
first it helps to rewrite 3/sqrt6 as sqrt3 / sqrt2
How’d u get this
from there you would find it useful to perform certain manipulations (i.e. factorization) as well as rewriting other expressions in terms of trig identities
Alr thx
Still, we arrive at the same result
dude you randomly replaced a sin10 with a cos10
don’t act all arrogant when helping someone when your work is just nonsense
I’ll try to do it tomorrow
Oh, yeah. I have done a typo, my bad
Without typo lol
3/sqrt(6)*cos(10) becomes 3/sqrt(3)*sec(45)*cos(10)
then what
and where did the 3 go
3/√(6) = (√(3)/√(2))
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how are P1 and P2 negitive?
Cause they're downwards what?
how do they know its a clockwise moment?
Find the pivot point
Cause we're analyzing joint A
Then just imagine what direction it’ll be turning in if you pushed at that point
ah gotcha
Consider pulling onto point B in the direction of P1, with A as your pivot
so when im doing my own work, when should I make clockwise or counter clock wise positive
You don’t need to
Just put all clockwise torques on one side
And counter on the other
am I over thinking this
Maybe lol
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is b) correct?
i did it with my friend but i feel like the right answer would be
10sin(5x)cos(5x)
yea thats right
ur answer
but if u apply the sin(2x) identity
given sin(2x) = 2sin(x)cos(x)
we see that 10sin(5x)cos(5x) = 5 * 2sin(5x)cos(5x) = 5*sin(10x)
which is also the answer given in the screenshot
i dont think so
theyre differentiating btw
soooo
is both answers correct?
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hi there could i get my solution reviewed for q2
so what I did was first start off by finding r'(t) so I can solve int_c F(r(t)) dot r'(t) dt, then just went on to solve integral from there
The logic looks good. Did your answer get rejected or something?
nope i don't have the solution, just wanted to check if my steps were correct.
thanks
.close
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@thin gulch
ok, what's your thought?
For the function to be defined I have found the domain of the roots and it's -1<x>1
Now since both are positive, i have done a cross multiplication
(the denominators)
for sqrt(x^2-1) only, but yes that's the right start
Yeah, the other one is always positive
ok so you have
$x \sqrt{x^2-1} > x \sqrt{x^2+1}$
lgkoo
also I think you meant to say x>1, and x<-1, not -1<x
without any explanation I actually cannot follow your work, not a single word is written, such as when/if to test different scenario. It's important to write down your thought because examiners and ppl cannot read mind and you don't want them to be confused.
Okay i will try to put the words
ok I think I know what you're doing. So the hint here is: since we know sqrt(x^-1) is not defined for -1<x<1. Consider the two cases: x>1 and x<-1 separately
Okay a minute
What is it ?
you are right that $\sqrt{x^2-1} - \sqrt{x^2+1} < 0$ for x > 1
lgkoo
lgkoo
is a product of positive and negative
@thin gulch
correct
So the final answer will be the intersection of the domain of root and the answer we got now ?
yeah, which is just x<0
But the book mentions the answer as -1>x>1
Guess it's vogue ?
-1>x>1? That cannot even be true, how can -1>1?
Sorry, i mistyped. -1<x<1
@thin gulch
ok, but that's just the region where x/sqrt(x^2-1) is undefined. Can I see the question?
!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.
Q. 11 @thin gulch
But how is x>1 ?
So, the book answer is vogue because the solution and graph both disproves it ?
uhh I'm not sure what vogue means, but the book answer is wrong
Thanks, can you please mention the tool that you used to acquire the graph ?
ofc
it's desmos
Thanks, problem solved
you're welcome
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#29
try using the substitution of u = sinx
Optimistically I want to say that's a typo and it should be sqrt(1-sin^2) as then it's a super easy simplify and subtitute but maybe it's just obnoxiously hard lmao
yes i agree with taybee
uh what does this do
i also forgot to change limits of integration but thats ok
,rotate
😭😭😭😭😭
you can then write cos(x) in terms of sin(x) then in terms of u
$\cos(x) = \sqrt{1-sin^2{x}$
lgkoo
Compile Error! Click the
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so $cos^3{x} = (1-\sin^2{x})^{\frac{3}{2}}$
how would i get it in terms of u
lgkoo
remember our substitution is u=sinx
the result looks ugly but the process isn't too difficult once you see the right substitution to make
alright what now
how would u integrate ((1-u^2)^3/2)/√(1-u)
c'mon I've seen you helped ppl a lot, you can spot how to simplify this
hmm lemme see
hint: what does (1-u^2) factorise to
uh
LMAO its simple cancellation
😉
u r a genius
i forglorb
thx, but I'm really not XD
(1+u)(1-u)?
yup
so you have to integrate (1+u)^(3/2) * (1-u)
any idea what the method for this is?
uh integration by parts?
yup
hmm I don't think it makes too much of a difference when doing the by parts
I feel like you're more likely to make mistake by making another substitution
but if you're confident, go for it
i’ll try
I think he means u as in one can write the parts formula as uv - int(vdu) rather than making a second u-sub
To which I would say, yes, that is the one I would differentiate XD
ohh
yeah absolutely, differentiate 1-u
i came to a conclusion
im not@gonna bother simplifying it all the way
so i just finished integration by parts
substituted the values
and boxed the answer
profs fault for giving such hard question 🗣️🗣️
hahaha honestly fair enough
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am i missing something?
cant i just plug in 7 and be done
yes
not in this case
That just means the limit approaches from the positives, it doesn't change anything in terms of this specific example
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wot have u tried?
i tried combining the fractions in the brackets
but in the end it got me to 3/x * 1
^
try combining the fractinos in the brackets again
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what would be the proof for this?
I dunno if this is right
prolly smth easier
but u could let A be [[e,f],[g,h]] and then let X be [[a,b],[c,d]]
where a, b, c, d, e, f, g, h are in the reals
and then do matrix multiplication
like just set arbitrary matrices?
ok i will give it a go
the nice way is to test for some specific matrices X only
if you plug in a matrix X, it will give you some equations (linear equations this time, so much less disgusting than just putting two arbitrary matrices like poggers) that the entries of A must satisfy
if you choose your Xs smartly, you can get to the result fast
wdym by test for specific matrices X only?
our premise is that we have a matrix A such that for all X, AX = XA
we're free to pick whatever X we want, for example X = [1 0 ; 1 1]
and we know that A [1 0 ; 1 1] = [1 0 ; 1 1] A from our premise
this tells us some information on the entries of A
so u can choose X to be whatever u want?
I thought the point was to show that it works for all real 2x2 matrices X
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How can I use both similar triangles as well as pythagoras theorem to get b)
@limpid mulch Has your question been resolved?
@limpid mulch Has your question been resolved?
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someone break this down conceptually how to solve this using chain rule
why did you open another channel
i thought u were afk
oh.
Help renz plz
Renz
you cant combine exponents like that
in that example, you can only combine 2 and -2
,,-4e^{(1-x)^2}(1-x)
Renz
thats the derivative
it cant be further simplified i believe
just multiply the 2 and -2 together, and put it in front
now lets do these
ah oki
im asking what was ur thought process for knowing what to do
this specifically
im still kinda confused
chain rule is taking derivative outside, leaving inside function * taking derivative of inside function
Ah alright leme give you an example
with exponentials
Ok
$e^{x^2+2x}$
Renz
how would you differentiate that
power rule first?
the first thing you gotta do is to write it down again
since the derivative of e^x is itself
so
wait but
ye?
yea but
e^x is like the parent function
so you will be doing the same
write the thing again, but this time, you have to multiply it by the derivative of the exponent
yea thats right
Ok ty
oh and the original example i gave you was wrong
instead of 2e^(1-x)^2
it was 2e^(1-x^2)
however i did what u told me
is this right
$e^{1-x^2}$
Renz
why do we not do anything with the 2
the one thats being multipled to this
do we not use product rule or anything when solving for the derivative???
its just a constant being multiplied
cause i swear that constant would be 0
so no need to worry about it
Renz
the 5 is a constant
derivative of that would be 2x
you can factor that out from the derivative operator
10x
Renz
Renz
the point is, the thing being multiplied was just a constant
you will only apply product rule if its a variable that is being differentiated
for example
,,(5x^2)(x+2)
Renz
Renz
there you have to apply product rule, since both factors have x in it
,,(e^x)(sin\pi)
Renz
but if you have smth like this
i didnt know this was a thing 😭
ty so much
you can just differtiate e^x and multiply sin(pi)
since sin(pi) is just a constant
yea
just remember, you can only factor out constants
that will be more common once you get to integrating stuff
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yw
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hey im back again
can you help me find the derivative of this
did i do something wrong?
quotient rule i used
3^(2t)/t
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Are a and x the same thing here?
a is the point you're looking at for the limit, here it's -1
whereas x is a variable that can move around
so x and a are the same thing here?
no
You're ignoring a lot of that sentence
At the point x = -1, continuity is violated.
That doesn't mean x is now fixed to be -1 for all further occurrences of x
oh
f(-1)=-3, and the limit as x approaches -1 at least from the left side is 3
and as it approaches from the right side its -3
so is the limit non existant
Yep! That's true
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There wasnt one for the question though
Is the reciprocal of the graph on the right correct?
Isnt there supposed to be a third graph in the middle or no?

