Rose86
Badges: 1
Rep:
?
#1
Report Thread starter 3 years ago
#1
Name:  IMG_7497.jpg
Views: 82
Size:  500.4 KB
0
reply
Zacken
Badges: 22
Rep:
?
#2
Report 3 years ago
#2
(Original post by Rose86)
[...]
What have you tried? For the first part: can you see why a\neq 0? (hint: \inf(A) > 0)
0
reply
Rose86
Badges: 1
Rep:
?
#3
Report Thread starter 3 years ago
#3
(Original post by Zacken)
What have you tried? For the first part: can you see why a\neq 0? (hint: \inf(A) > 0)
Yes, but I dont know how to define C=...
0
reply
Zacken
Badges: 22
Rep:
?
#4
Report 3 years ago
#4
(Original post by Rose86)
Yes, but I dont know how to define C=...
You don't need to define C, the definition has been given to you?
0
reply
Rose86
Badges: 1
Rep:
?
#5
Report Thread starter 3 years ago
#5
(Original post by Zacken)
You don't need to define C, the definition has been given to you?
I mean I dont know how to use this equation C=1/a+...
0
reply
Zacken
Badges: 22
Rep:
?
#6
Report 3 years ago
#6
(Original post by Rose86)
I mean I dont know how to use this equation C=1/a+...
First off, it's not an equation. Second off, to ensure that the object (1/a) + b exists, that is, C is well-defined, you need to ensure that a \neq 0 where a is a general element of A. Can you see why this is true?

Second, you need to show that the supremem of C exists. What is your definition of supremem? How can you apply it here?
0
reply
Rose86
Badges: 1
Rep:
?
#7
Report Thread starter 3 years ago
#7
(Original post by Zacken)
First off, it's not an equation. Second off, to ensure that the object (1/a) + b exists, that is, C is well-defined, you need to ensure that a \neq 0 where a is a general element of A. Can you see why this is true?

Second, you need to show that the supremem of C exists. What is your definition of supremem? How can you apply it here?
Sorry, i used word equation because English is not my first Language
0
reply
atsruser
Badges: 11
Rep:
?
#8
Report 3 years ago
#8
(Original post by Rose86)
I mean I dont know how to use this equation C=1/a+...
If L = inf A > 0, then by definition, for all a \in A, a \ge L so how large can 1/a become? How large can \frac{1}{a}+b become?

It may help if you think of a specific set A with a positive infimum e.g. A=(\frac{1}{10}, \infty)
0
reply
atsruser
Badges: 11
Rep:
?
#9
Report 3 years ago
#9
(Original post by Zacken)
What is your definition of supremem?
I guess it's the same as the definition of supremum?
1
reply
atsruser
Badges: 11
Rep:
?
#10
Report 3 years ago
#10
(Original post by Rose86)
Sorry, i used word equation because English is not my first Language
We really ought to use a different symbol here, to indicate a definition, rather than equality. Often people write C := \{ \cdots \} to show this.
0
reply
Rose86
Badges: 1
Rep:
?
#11
Report Thread starter 3 years ago
#11
(Original post by atsruser)
If L = inf A > 0, then by definition, for all a \in A, a \ge L so how large can 1/a become? How large can \frac{1}{a}+b become?

It may help if you think of a specific set A with a positive infimum e.g. A=(\frac{1}{10}, \infty)
I know that when I put bigger and bigger number then it will be arbitary close to zero, nacer will be zero
0
reply
DFranklin
Badges: 18
Rep:
?
#12
Report 3 years ago
#12
(Original post by Rose86)
I know that when I put bigger and bigger number then it will be arbitary close to zero, nacer will be zero
The question was how large 1/a can become, not how small...
0
reply
Zacken
Badges: 22
Rep:
?
#13
Report 3 years ago
#13
(Original post by Rose86)
I know that when I put bigger and bigger number then it will be arbitary close to zero, nacer will be zero
To complement what the others are saying, in a purely unrigorous, informal way - the intuition here should be: you want to make (1/a + b) as big as possible. Which means making b as big as possible and (1/a) as big as possible. To make the latter as big as possible, you should make a as small as possible, etc...
0
reply
Rose86
Badges: 1
Rep:
?
#14
Report Thread starter 3 years ago
#14
(Original post by Zacken)
To complement what the others are saying, in a purely unrigorous, informal way - the intuition here should be: you want to make (1/a + b) as big as possible. Which means making b as big as possible and (1/a) as big as possible. To make the latter as big as possible, you should make a as small as possible, etc...
Thank you
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of East Anglia
    PGCE Open day Postgraduate
    Sat, 29 Feb '20
  • Edinburgh Napier University
    Postgraduate Drop-in Brunch Postgraduate
    Sat, 29 Feb '20
  • Teesside University
    All faculties open Undergraduate
    Sat, 29 Feb '20

Do you get study leave?

Yes- I like it (374)
59.08%
Yes- I don't like it (34)
5.37%
No- I want it (180)
28.44%
No- I don't want it (45)
7.11%

Watched Threads

View All