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# TIFR 2015 Problem 7 Solution -Increasing Function and Continuity  TIFR 2015 Problem 7 Solution is a part of TIFR entrance preparation series. The Tata Institute of Fundamental Research is India's premier institution for advanced research in Mathematics. The Institute runs a graduate program leading to the award of Ph.D., Integrated M.Sc.-Ph.D. as well as M.Sc. degree in certain subjects.
The image is a front cover of a book named Introduction to Real Analysis by R.G. Bartle, D.R. Sherbert. This book is very useful for the preparation of TIFR Entrance.

Also Visit: College Mathematics Program of Cheenta

## Problem:

Let and be two functions from to with strictly increasing. Which of the following statements is always correct?

A. If (g) is continuous, then is continuous

B. If  (f) is continuous, then is continuous

C. If (f) and is continuous, then (g) is continuous

D. If (g) and are continuous, then (f) is continuous

## Discussion:

A: Let (g(x)=x) for all .

(f(x)=x) for and (f(x)=5+x) for .

Then and (f) is not continuous.

So A is False.

B: Reverse (f) and (g) in A to show that B is False.

C: If (f) and are continuous then (f) is 1-1 (increasing), continuous map ([0,1]to [0,1]).

(A subset [0,1] ) be closed. Then (A) is compact. (Closed subsets of compact spaces are compact).

Therefore (f(A)) is compact. (continuous image of compact set is compact).

We have that (f(A)) is a compact subset of ([0,1]). Therefore (f(A)) is closed in ([0,1]). (compact subspace of Hausdorff space is closed).

Therefore, (f) is a closed map. So is continuous.

Hence is continuous.

So, C is True.

D: Let for all .

(f(x)=x) for and (f(x)=5+x) for .

Then for all .

So is continuous but (f) is not continuous.

So, D is False.

## Helpdesk

• What is this topic: Real Analysis
• What are some of the associated concept: Continuity,Closed Set, Compact Set
• Book Suggestions: Introduction to Real Analysis by R.G. Bartle, D.R. Sherbert TIFR 2015 Problem 7 Solution is a part of TIFR entrance preparation series. The Tata Institute of Fundamental Research is India's premier institution for advanced research in Mathematics. The Institute runs a graduate program leading to the award of Ph.D., Integrated M.Sc.-Ph.D. as well as M.Sc. degree in certain subjects.
The image is a front cover of a book named Introduction to Real Analysis by R.G. Bartle, D.R. Sherbert. This book is very useful for the preparation of TIFR Entrance.

Also Visit: College Mathematics Program of Cheenta

## Problem:

Let and be two functions from to with strictly increasing. Which of the following statements is always correct?

A. If (g) is continuous, then is continuous

B. If  (f) is continuous, then is continuous

C. If (f) and is continuous, then (g) is continuous

D. If (g) and are continuous, then (f) is continuous

## Discussion:

A: Let (g(x)=x) for all .

(f(x)=x) for and (f(x)=5+x) for .

Then and (f) is not continuous.

So A is False.

B: Reverse (f) and (g) in A to show that B is False.

C: If (f) and are continuous then (f) is 1-1 (increasing), continuous map ([0,1]to [0,1]).

(A subset [0,1] ) be closed. Then (A) is compact. (Closed subsets of compact spaces are compact).

Therefore (f(A)) is compact. (continuous image of compact set is compact).

We have that (f(A)) is a compact subset of ([0,1]). Therefore (f(A)) is closed in ([0,1]). (compact subspace of Hausdorff space is closed).

Therefore, (f) is a closed map. So is continuous.

Hence is continuous.

So, C is True.

D: Let for all .

(f(x)=x) for and (f(x)=5+x) for .

Then for all .

So is continuous but (f) is not continuous.

So, D is False.

## Helpdesk

• What is this topic: Real Analysis
• What are some of the associated concept: Continuity,Closed Set, Compact Set
• Book Suggestions: Introduction to Real Analysis by R.G. Bartle, D.R. Sherbert

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