#help-49
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for the given norm
then how can I construct an example to show the space is incomplete
the idea is that you might have functions whose values become smaller but whose derivatives explode, and that's how your limiting function ends up outside C^1.
er
ok not exactly "limiting function ends up outside C^1"
ok sorry i messed up a little
give me a function that belongs to C^0 but not C^1
ln x
on [0,1]?
$\sqrt{\left(x-\frac{1}{2}\right)^{2}+\frac{1}{n}}$
Xyrokryen
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i found fxx fyy and fxy but im kinda lost in D=fxx*fyy-fxy^2
Show how you got this D
well fxx=-6x fyy=(3xe^y)-(9e^3y) fxy=3e^y
D=fxx*fyy-fxy^2
Try factoring D
for fyy=(3e^y)(x-3e^2y)
That's not D
oh D
i mean i could just find solution for D
for the given values
(-18x^2)(e^y)+(54xe^3y)-9e^2y
@fallow scarab sorry if i shouldnt mention you
?
like this?
Yea just stop pinging me
sorry
This isn't factored
Factoring is like 3+9 = 3(4)
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can someone help idk where to start
what is property 10
is this stewart
yes
can you please show property 10
this is the first time the book mentions it
Doubt
this is property 10
Lmao
ok
can you solve it now
i'll try
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so im kinda confused with this problem
idk where to start
okay
lets consider the max value of sqrt{4 - x^2y^2}
since x^2y^2 always >= 0
-x^2y^2 always <= 0
therefore
4 - x^2y^2 <= 4
for area of the first one
its just
a circle
second one
use the fact that -1 <= sinx <= 1
area is triangle
wait
why
my math teachers send my class this
Is there a set whose size is strictly between that of the integers
๐
N and the real numbers
๐
R?
idk how to solve
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sorry
its okay!
well yeah this makes it better but in a test im not allowed to use desmos
if i square a negative
what will i get
yeah my bad
a^2?
its a known inequality
so i just have to know that
(-5)^2
yeah 25
1
u should know that if u're doing calc 3...
i mean yeah-
i suck ๐ญ
whats ap and bc
yeah
for both x and y?
like from this inequality
kinda contradicting
${(xy)^2 \geq 0 \implies -(xy)^2 \leq 0}$?
k
x can be both - and + right
yeah so i agree
k
i made a mistake ๐ฅ
this
still agree
question tho
x^2 + y^2 leq 1
so why did we look for this like is it a standart procedure for this type of exercise?
for (xy)^2 => 0
its a great way to find max/min
ahh ok
isnt it the minimum?
why do u think its the minimum
well because of this
the lowest we can go is 4
if it was 0 for x^2 + y^2
lowest or highest
lowest but i feel like thats wrong and idk why
the expression is always less than or equal to 4
so 4 is the maximum inside the square root
oh yeah true
now
to the minimum
we have to be wary of our constraint
x^2 + y^2 <= 1
for the minimum
we want the highest value of (xy)^2, right?
k
yes
notice how (xy)^2 brings the value down as it increases?
yeah
i just tried it
i mean goes both ways
because -2 for x and y would give the same result as +2
.
ok so -1 0 1
doesnt have to be that
yeah i know im just saying
ok so
from x^2y^2
and x^2 + y^2 = 1
we can rewrite the final eq as
x^2(1 - x^2)
the maximum (xy)^2 lies on the border of the area
all i know now is this, beyond this im confused
yes
to find min, we must maximumze x^2y^2
yeah
they are infinite tbh
x^2 + y^2 <= 1
oh yeah
like 1 and 0
yes, like 1 and 0
we know that it is on the border
but where on the border?
to do that
so we want 2 values that are close to this
hence 1 and 0
yeah
it had to do with this right
recall that x^2 + y^2 = 1 means that y^2 = 1 -x^2
ye, our x and y are restricted by this
no i meant the 1 and 0
so what we seek to maximise is now x^2y^2 = x^2(1-x^2)
they are within that inequality, yes, but arent the correct answer
yeah
ok
do u know how to maximise x^2(1-x^2) from calc 1
ok how did we go here
y^2 = 1-x^2
substitute y^2
with what
1-x^2
1?
using calc 1 techniques
i cant recall ngl
x^2 - x^4
derivative
2x - 4x^3
find critical point set = 0
2x(1-2x^2) = 0
2x(1-sqrt{2}x)(1+sqrt{2}x) = 0
critical points are 0, -1/sqrt{2}, 1/sqrt{2}.
in the question, we are considering only for x >= 0
therefore
x is either 0 or 1/sqrt{2}
cant be 0
evidently
so lets check if 1/sqrt{2} is our max
do a second derivative test
2 - 12x^2
gives - 4
so it is the max
${x^2y^2}$ is maximum at ${x = \frac{1}{\sqrt{2}}}$
k
where did we get x^4
$x^2(1-x^2) = x^2 - x^4$
k
wdym
thats fine. ur not bothering
here
factorisation of 2x - 4x^3
can you write this as latex please
[ 2x(1-\frac{1}{\sqrt{2}}x)(1+\frac{1}{\sqrt{2}}x) = 0 ]
k
,w 2x(1-2x^2) = 0
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u good m8?
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(algebraically)
i just graphed it to make it easier to under stand ๐
i am so not doing this right now
can you show me out the steps
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Did I do this right
Did you do the desmos thing
I don't get the function
Your critical point at 4/5 seems a little off
The limits all seem right tho
lmao w?
Yeah ok the graph seems right
Lmao is my personal prefix lol
oh
Use ,w if you wanna use it
this just seemed a bit wonky since i couldnt find y values
well i may have overlooked that part a little
Nice work
all the limits look good?
Lolol fr i dont even look at inflection pts while drawing
Just the crits
i should start doing the crits first
Yes the limits look good
Yeah
could you help me with the next problem
K
Man this is nice hw i like it
I used to have hw like this when i was learning these topics
But i never did it
Cos i was too lazy

bro this is literally so easy
I'm brain dead tho
Don't.
i am not exaggerating, in india even a 8th class can student do this , (8th class student is like 13 yo)
<@&268886789983436800>
am sorry am i violating any server rule
If you can't say anything helpful, say nothing.
do not belittle anyone over difficulty of a problem
๐ญ๐ญ
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6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
setup
So, the volume formula for this is V = lwh, where l is length, w is width, h is height.
just curious , is this college level mathematics in usa? also just solve it by using l=2b
calc in college
So, we can start filling things in.
this is calculus?
The volume is 30. The length is 2w.
V = lwh
30 = 2w^2h.
So, what is h in terms of w?
Leave the channel, please.
why is 2w to the power of 2h
It's to the power of 2.
Exponents come before multiplication in PEMDAS or BODMAS.
(30 = 2w^2h)
Chai T. Rex
oh it seemed like the h was in the exponent the way it was typed
Nope
The way it was typed seemed like it was not in the exponent
Otherwise there would have been a pair of brackets, i.e. w^(2h)
So, solve that for h. What do you get?
15/w^2
OK, good.
Now we have everything in terms of h.
Now we need to look at the sides.
Oh, sorry in terms of w.
The bottom is the length times the width.
So, the bottom is lw, which is 2w^2.
can we not calculate h by taking diagonal of the box?
What is the area of one of the sides?
what
Well, you said that h = 15/x^2.
yes
wym put in terms of x
<@&268886789983436800> Shark is a troll that was told to leave.
there are 2 variables in this question
how is this troll , see it yourself
value of x is not given
this channel is occupied by someone else right now nevermind didn't see previous context
for someone who claims this is easy you sure are frickin it up
That's not helpful either
It's best to assume they're just watching the channel interested in the problem despite the earlier comments.
Hm alright i apologise
im lost rn
You said xh is one of the sides, right?
And h = 15/x^2.
So, what you can do is to substitute 15/x^2 for h, like this: x(15/x^2).
Does that make sense?
15/x?
Right.
You said the other side was 2xh.
What do you get after you substitute 15/x^2 for h in that?
there is no such side as xh its x and 2x sir
I see you can't help yourself but comment on this, so let me help you resist the urge to keep interrupting.
We'll see that in a minute.
im confused what im doing
so h=hx?
yes
You also said that h = 15/x^2.
So, we're going to use substitution, which means we can replace one side of an equation with the other.
So, we can see h = 15/x^2 is an equation with h on one side.
We can see that xh is the area of one of the sides.
but h is the hight and hx is an area
Right.
We want it to only have one variable, though.
Right now that area has two variables in it.
are you trying to tell me hx=15/x^2
No.
We got that h = 15/x^2, not hx.
Now that we know that, we can change h to 15/x^2.
So, if we had 7h or something, that would be 7(15/x^2).
If we had h^2 + h, that would be (15/x^2)^2 + (15/x^2).
What I'm doing there is replacing h with 15/x^2.
Does that make sense?
little
5
Right, and you used substitution there.
x + y
2 + 3
5
You replaced x with 2 because x = 2.
yes
You replaced y with 3 because y = 3.
You can also do that on more complicated things.
Oh thats a good way of explaining imma steal that
how is this related
oh i substitiute in 15/x^2 for h then the x tags along
same with the othe
Right, what do you get for 2hx?
30/x
OK, good.
Now we want to figure out prices.
The base (the bottom side) is $15 per square meter.
The area of the bottom is 2x^2.
So, what's the price of the base in terms of x?
How did you get that?
Oh, I see.
No, that's not the way to do that.
x isn't the area.
If you have a price per area and an area, you do price/area * area.
That'll give you the price.
(\frac{\text{price}}{\text{area}} \cdot \text{area} = \text{price})
Chai T. Rex
i know that]
OK, so we have the price/area as $15/m^2.
We have the area as 2x^2.
So, 15 * 2x^2 = price.
price/area * area = price.
Does that make sense?
No, x is a length, right?
So, you can't fill in $15 for x because that's a price, not a length.
They give us two prices per area.
$15/m^2 for the bottom.
$4/m^2 for the top.
m is meters, which is a length.
So, m^2 is an area.
Right.
Now you used price/area * area to get price.
There's a small mistake.
Remember that there are four sides.
Ok
You have only two there.
OK, and you can also add the first two together.
Ok
So, we have the price as 360/x + 30x^2.
yes
Now we want the cheapest, so we want to minimize the cost.
So, how can we find minima using calculus?
dirive
Right, we can differentiate it.
this is calc?
yes
So, what's the derivative of 360/x + 30x^2?
dang 9th grade gonna be easy
find x
Well, we can find x, but we need an equation for that.
Right now we don't have an equation (with =), we only have an expression.
What happens when you reach a local minimum is that it comes in from the left going downwards, then it goes off to the right going upwards.
,w plot x^2
Like the minimum there has the graph coming in from the left going downwards.
Then it has the graph going on to the right going upwards.
yes
So, the derivative tells you the slope, right?
yes
On the left of the minimum, the slope is negative.
On the right of the minimum the slope is positive.
What's the slope at the minimum?
0
thats what i ment when i said find x
to be honest im blanking on algebra,lol
multiply by x2
Right, so multiply both sides by x^2. What do you get?
this seems wrong but i got cube root of 6
Yes, substitute that into the price formula we got.
is that the same as 6^(1/3)
Yes.
just checking
1/n as an exponent is the nth root.
Yes, that's correct, but unless they want you to put it in the form of a decimal, you should do (90 \cdot 6^{\frac23}).
Chai T. Rex
Lol i didn't expect the answer to be so cursed looking at the question
tbh i dont know if i would be able to do a similar question
OK, so we got the minimum price.
We just need the dimensions (don't forget to put m for meters).
Just resolve this twice after finishing rn
You'll get the hang of it
One time looking at soln one time without
how do i find this
OK, so we had this ^
So, the length is 2x, the width is x, and the height is 15/x^2.
How did you get 8.25 for the height?
Oh, I see.
Remember that it's 15/x^2.
Not 15/x.
@wary ferry
You can also check by multiplying all three together to see if you get the volume of 30 the problem has.
@wary ferry Has your question been resolved?
I see
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3
In the book, were told to assume that x, y, and z are nonnegative, but I got z = -6.
btw when I write circle(number, number) -> ..., it means that iโm using those equations to get a new equation
and an arrow pointing into a circle with a number means ill later refer to that as equation ...
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<@&286206848099549185>
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for all $n$, prove that $\sqrt[n]{\sqrt{3}+\sqrt{2}}+\sqrt[n]{\sqrt{3}-\sqrt{2}}$ is irrational
skissue.in.a.teacup
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@viral dagger Has your question been resolved?
did you try recurrence relation and induction?
I remember doing this for case n = 100, I'm not sure this is exactly right, it may help though
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@molten bay Has your question been resolved?
<@&268886789983436800>
g(z)=10 z^3 and h(z)=e^z -z+1/z-4 since in rouche theorem |g(z)| > |h(z)| and f(z)=g(z)+ h(z) , f(z) and g(z) are analytical function
f(z) and g(z) have the same number of zeroes (counted with multiplicity)
How will you check it satisfied the condition of
|g(z)|>|h(z)|
This function has a singularity (pole) at ๐ง=4 because of the term 1/z-4 and then |z|<4
โ
you can check it?
The choice of ๐(๐ง) and โ(๐ง) in Rouche Theorem depends on the value of โฃ๐งโฃ
I took this in order to find number of zeroes
this is true for |z|=2,3
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I need help if anyone knows how to use desmos. I need to graphic a harmonic series (sum of 1/n or wtv) but I also need to show a bar graph of all individual squares under the function and kinda show how they add up and round off? does anyone know how to do that
you could use 0 <= y <= 1/N {N <= x <= N+1} or sth like this
can you please show me how to do this but with all the boxes adding up together?
thats the part I cant really figure out
wdym by adding up?
like stack them on top of each other?
yes
like its supposed to show that if you keep adding individual blocks it will follow the curve of it
but idk how bro
oh logarithm curve
Maybe I could use 2 colors to distinguish the individual boxes?
so thaat its not just one big red box
either way is fine
okay
ill use these 2
hold on
the way im doing it will take ages to compute
im thinking of doing it recursively
is this what you meant?
yes how did you do this
it takes ages to render though, computing that sum is terrible
maybe i could define new sequence
hold on
the first 10 is fine but does L have to be the end of the sequence?
You can define L to be as high as you need it to be
just make it even or else it will break i think
ill prob just do 10 I just need a screenshot of a sectino of the graph
im just gonna change the variables that shouldnt be an issue right cuz im using n as a list of 10k terms to generate the series as a dotted curve
yeah, it shouldnt
wait is this simplier if its one color?
oh you dont even need N
Possibly
like
I just needed something like this
but with series of 1/n
this is how it looks with one color
it doesnt look as bad as i thought it would
oh because im using a different way than i originally intended
makes sense
is that just with the one box instead of subtracting two ?
Yeah
instead of spliting it to N1 and N2, its just N
is there anyway I can see the equation for that?
yea understood
sorry for overcomplicating it to you
sure
and this is H
H is basically harmonic sum up to N
yes this works perfectly thank you
yea I read that somewhere but im only in calc 1 its alright
the sum is between ln(x) + mascheroni and ln(x+1) + mascheroni, so ln(x+0.5) + mascheroni is quite a good approximation
ok tysm
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why does order get reversed when we transpose a product of matrices
Yep
cool lol
idk what are feynman path integrals tho
will learn all that i guess
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Explain like im 5
If dx= 1/10
And x= 100
Shouldnt x+dx= 100+10/100 or just 100+10?
And what If dx = 1/100 instead of 1/10
Would it still look like 100+1?
100 + 10/100 isn't 100+10
get your arithmetic checked,
and 100+1/100 would be 100.001
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I started off by finding the eigenvalues of T
which were ยฑi
so I thought that x^2+1=0 is a polynomial satisfying this
So the minimal polynomial is x^2+1
Yeah, thatโs the minimal polynomial
no way thats how axler intended this
you are supposed to use the construction from the proof
thanks
I dont know how many results he covered about the relationship between the eigenvalues and the min poly
this is how axler cover the construction
There is also "Eigenvalues are the zeros of the minimal polynomial"
which has been covered
thats not enough to recover the min poly
this too
you need to argue that the eigenvalues arent repeated in our case
but still, I very much doubt that you are supposed to do this with the eigenvalues
okay, I'll try constructing it similar to the proof
The proof way would require me to construct tha matrix instead and work with that, right
I suppose this method works too
the Matrix is $\begin{bmatrix} 0&-1\1&0 \end{bmatrix}$
wai
so T(e_1)=e_2
T(e_2)=-e_1
T^2(e_1)=T(T(e_1))=T(e_2)=-e_1
this gives is the minimal poly is x^2+1
I think I'm getting it
thanks
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if |z|=1 then how can we check |e^z|<=e?
try using z = a + bi
and think about what |e^z| becomes
yes it is circle at orifign
the a is the x-coordinate
which point means?
which x-coordinate can appear on the circle
(1,0)
This is the point with largest a, yes
yes
it can be also shown that the lower bound is e^(-1)
or 1/e
since the leftmost point is (-1, 0)
np
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I'm applying argument principal here but what will be roots of this polynomial?
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solve over reals
$$\sqrt{6x-2} = 2 + \sqrt[3]{x+5}$$
acgn
do you know how to proceed from here?
@neat silo Has your question been resolved?
3
wat
Yes
wait
x = 3 is a sol
ok
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Just wanna check that my proof is correct
when i multiply 4b^4(a^4) do i get 16b^4 a^4 or 16a^4 b^4??? or is it same thing
!occupied
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your last two products are equivalent btw
alr
yay
Mkay
I'm sorry if I'm being paranoid but that is sufficiently small |z|, right?
Oh wait
๐
Haha I think I screwed up the proof a tiny bit
$|p(z)|=|a_0+a_1z\ldots a_nz^n|\le|a_0|+|a_1z|\ldots|a_nz^n|=a_0+a_1|z|\ldots a_n|z|^n\le a_0+a_1\ldots a_n\le K$ for some $0<|z|<1$ and $K\ge\sum_{k=0}^n a_k$, $K>0$, which means that since $|z|$ is sufficiently small that $p(z)=O(1)$ as $z\to 0$ by definition.
;(
And a K will always exist, since the sum is finite
Yipee
I'm a little stuck on the second question though
How do I show that $a_0+a_1|z|\ldots a_n|z|^n\le K|z|^n$ for sufficiently large $|z|$?
;(
Oh wait
๐
I can show that
$\frac{a_0}{|z|^n}+\frac{a_1}{|z|^{n-1}}\ldots a_n\le K$ for sufficeintly large $|z|$
;(
AHAHHAAH
ezpz
Since $|z|$ is large (and hence 0<$\bigg\vert\frac1{z}\bigg\vert^n$<1) we have that every term will tend to zero and hence all we really need is $\frac{a_0}{|z|^n}+\frac{a_1}{|z|^{n-1}}\ldots a_n\le K$ which is now trivial!
;(
Yeah we can just let $K\ge\sum_{k=0}^n a_k$, $K>0$ again can't we
;(
why does it say for some 0 < |z| < 1
shouldn't it be for all such z's?
or, replace every |z|^k by |z|^n
uh, I may be going crazy, but why is it fine to pull the $a_i$ out of the norms? it can be the case that $a_i<0$, right?
00100000
Convienience
|a_i| always
I forgor ๐
it sounds like your inquality only holds for some z's and some K's
but you need for all z's for the limit to work
But |z| is smol?
you said your inequality holds for some 0 < |z| < 1
what if it's only 0.5
and it doesn't hold for any other z's
Ohhh
then you don't have the result that p(z) is in O(1)
Alright
that's the same statement as before
I think I just jumped ahead with the wording ๐
$|p(z)|=|a_0+a_1z\ldots a_nz^n|\le|a_0|+|a_1z|\ldots|a_nz^n|=|a_0|+|a_1| |z|\ldots |a_n| |z|^n\le |a_0|+|a_1|\ldots|a_n|\le K$ for all $z$ such that $0<|z|<1$ and $K\ge\sum_{k=0}^n|a_k|$, which means that since $|z|$ is sufficiently small that $p(z)=O(1)$ as $z\to 0$ by definition.
By the same logic as the previous exercise we have that $|p(z)|\le |a_0|+|a_1| |z|\ldots |a_n| |z|^n$. Since $|z|$ is large (and hence 0<$\bigg\vert\frac1{z}\bigg\vert^n$<1) we have that every term containing $\frac1{|z|}$ is small and hence $\frac{a_0}{|z|^n}+\frac{a_1}{|z|^{n-1}}\ldots a_n\le K\implies |a_0|+|a_1z|\ldots |a_n| |z|^n\le K|z^n|$ for $K\ge\sum_{k=0}^n |a_k|$. Therefore $p(z)=O(z^n)$ as $z\to\infty$, by definition.
isn't the first part of the problem just an equivalent statement to ``for all $a_i$, there exists some $C$ such that $\limsup_{z\to 0}\frac{a_0+\ldots+a_nz^n}{C}<\infty$"? Then, since $\limsup$ is linear and each $a_iz^i$ approaches 0 as $z\to 0$, blah blah blah
00100000
I might be going crazy
I've been going crazy a lot recently
so take my fuckery with a grain of salt ๐
Ok
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Am I tripping or is factorisation the best way to solve this
nvm
$T^5+2T^4-7T^3-6T^2+5T+4=0$.\
Applying $T^{-5}$ to both sides \
$1+2T-7T^2-6T^3+5T^4+4T^5=0$
wai
why is that the min poly of T^-1
As the min poly of T is of degree 5 , T^{-1} has 5 eigenvalues as well, and thus is of degree 5
no
As T is invertible, all eigenvalues are non-zero
hmm
suppose it had a lower degree,applying T raised to the additive inverse of the most negative power to both sides, we'd get a poly of lower dgree than 5
like T^{-3}+T^{-2}=0 (say). applying T^3 to both dies we'd get T+I=0, violating the minimality
write that down properly
okay
Suppose the minimal polynomial had a lower degree than 5. say $m$. Applying $T^m$ to both sides of the minimal polynomial , we'd find that the minmal polynomial of T is of lower degree than 5, resulting in a contradiction
wai
Let $m(x)= a_ix_i$ be the minimal polynomial of $T^{-1}$. Suppose $m<5$. We thus have $\sum_{i=1}^{m} a_iT^{-i}=0$ . Applying $T^{m}$ to both sides gives us $\sum_{i=1}^{m} a_iT^{m-i}=0$.This would correspond to a polynomial of degree $m$ , violating the minimality of the polynomial of $T$
wai
awful
what's wrong
yes, just realised
Let $p(x)= \sum_{i=0}^{m} a_ix_i$ be the minimal polynomial of $T^{-1}$. Suppose $m<5$. Letting $x=T^{-1}$, We thus have $\sum_{i=0}^{m} a_iT^{-i}=0$ . Applying $T^{m}$ to both sides gives us $\sum_{i=0}^{m} a_iT^{m-i}=0$.This would correspond to a polynomial of degree $m$ . However $m<5$, and the degree of the minimal polynomial is given to be $5$, this is a contradiction. Thus the minimal polynomial of $T^{-1}$ must be of degree 5 or more.
Is this better
no
What's wrong?
.
literally right at the start is garbage
the name m is already taken
you cant use it for the degree
wai
Which expression
\sum_{i=0}^m a_i T^{m-i}
so it corresponds to a new polynomial q
yes
Let $p(x)= \sum_{i=0}^{m} a_ix^i$ be the minimal polynomial of $T^{-1}$. Suppose $m<5$. Letting $x=T^{-1}$, We thus have $\sum_{i=0}^{m} a_iT^{-i}=0$ . Applying $T^{m}$ to both sides gives us $\sum_{i=0}^{m} a_iT^{m-i}=0$.This would correspond to a polynomial,$q$, of degree $m$ . However $m<5$, and the degree of the minimal polynomial of $T$ is given to be $5$, this is a contradiction. Thus the minimal polynomial of $T^{-1}$ must be of degree 5 or more.
wai
Is this better
x^i, not x_i in the beginning
Let $p(x)= \sum_{i=0}^{m} a_ix^i$ be the minimal polynomial of $T^{-1}$. Suppose $m<5$. Letting $x=T^{-1}$, We thus have $\sum_{i=0}^{m} a_iT^{-i}=0$ . Applying $T^{m}$ to both sides gives us $\sum_{i=0}^{m} a_iT^{m-i}=0$.This would correspond to a polynomial,$q$, of degree $m$ . However $m<5$, and the degree of the minimal polynomial of $T$ is given to be $5$, this is a contradiction. Thus the minimal polynomial of $T^{-1}$ must be of degree 5 or more.
wai
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but what is the polynomial q
