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Easy functional equation (maybe)

Posted: Thu Feb 18, 2021 12:33 pm
by Asif Hossain
Find all $f : \mathbb{R} \rightarrow \mathbb{R}$ such that $\ f(f(x)) = f(x-1)+1 \ $

Re: Easy functional equation (maybe)

Posted: Fri Feb 19, 2021 1:53 pm
by Asif Hossain
Still no answer :roll:

Re: Easy functional equation (maybe)

Posted: Fri Feb 19, 2021 3:24 pm
by Safwan
Image[/img][/img][/img]
Asif Hossain wrote:
Thu Feb 18, 2021 12:33 pm
find all f:R->R such that f(f(x))= f(x-1)+1
Now you have to look at the problem from a different angle here
[img]
try inserting f-1(x) in the place where there's f(x) that should do it :)

Re: Easy functional equation (maybe)

Posted: Sat Feb 20, 2021 9:26 am
by Asif Hossain
Safwan wrote:
Fri Feb 19, 2021 3:24 pm
Image[/img][/img][/img]
Asif Hossain wrote:
Thu Feb 18, 2021 12:33 pm
find all f:R->R such that f(f(x))= f(x-1)+1
Now you have to look at the problem from a different angle here
[img]
try inserting f-1(x) in the place where there's f(x) that should do it :)
did you mean f-1(x) as inverse function?
How would you prove it has inverse?? Or the fuction is Bijective?

Re: Easy functional equation (maybe)

Posted: Tue Mar 30, 2021 5:22 pm
by Mahee2166
$f(x)=x$ This satisfies the equation. Right?

Re: Easy functional equation (maybe)

Posted: Tue Mar 30, 2021 9:10 pm
by Asif Hossain
Mahee2166 wrote:
Tue Mar 30, 2021 5:22 pm
$f(x)=x$ This satisfies the equation. Right?
satisfies but it is not only the solution it has infinite solutions :D

Re: Easy functional equation (maybe)

Posted: Sat Apr 03, 2021 1:57 pm
by Mahee2166
Asif Hossain wrote:
Tue Mar 30, 2021 9:10 pm
Mahee2166 wrote:
Tue Mar 30, 2021 5:22 pm
$f(x)=x$ This satisfies the equation. Right?
satisfies but it is not only the solution it has infinite solutions :D
How to solve this? I can not solve functional equations. Can amyone help by giving solution to this? Besides, can anyone suggest me any book to practice functional equation?

Re: Easy functional equation (maybe)

Posted: Sun Apr 04, 2021 9:25 am
by Mehrab4226
Mahee2166 wrote:
Sat Apr 03, 2021 1:57 pm
Asif Hossain wrote:
Tue Mar 30, 2021 9:10 pm
Mahee2166 wrote:
Tue Mar 30, 2021 5:22 pm
$f(x)=x$ This satisfies the equation. Right?
satisfies but it is not only the solution it has infinite solutions :D
How to solve this? I can not solve functional equations. Can amyone help by giving solution to this? Besides, can anyone suggest me any book to practice functional equation?
Read the note here, it may be helpful.
https://web.evanchen.cc/handouts/FuncEq ... -Intro.pdf