Math Is Fun Forum / Kurre's Exercises

Kurre · 2009-04-18 21:33:01

#1 Solve:
a)

b)

#2 Find all functions satisfying:

#3 Find all functions satisfying:

#4 Find all functions satisfying:

#5 Let a be a given real number. Find all functions satisfying:

#6 Find all injective functions satisfying:

Last edited by Kurre (2009-05-06 03:21:26)

Kurre · 2009-05-05 04:45:12

Well I would like to change the topic to "kurres exercises" or something, but I cant, so here comes a few more that are not related to functional equations.

#7 Let

Find expressed in A

#8 Let H be a subgroup of G. prove that the following statements are equivalent:
a) H is a normal subgroup
b) for all a,b in G, if and only if

#9 Solve the following equation in primes p,q,r:

Last edited by Kurre (2009-05-07 00:07:52)

mathsyperson · 2009-05-05 06:50:47

Changed! You can edit a topic's title by editing its first post.

Kurre · 2009-05-05 08:30:08

Thanks! But I still cant find a field where to edit the title? i know what u mean, i have seen it before. I thought it had been too long since i created the topic..

mathsyperson · 2009-05-05 09:03:26

Hmm. Maybe the software has changed then. I'm certain it used to be possible that way.
(It's how I changed the title, but I probably follow different rules)

Good point about my answer, I forgot about that detail. I can tweak it though!

JaneFairfax · 2009-05-05 18:50:17

mathsyperson wrote:
Changed! You can edit a topic's title by editing its first post.

You can edit a thread title for something like the first five minutes after you start the thread; after that period, you can’t edit the title any more (except for moderators).

I know, it’s hard for moderators to know all the problems that non-moderators go through.

mathsyperson · 2009-05-05 21:29:08

Thanks for clarifying!

Kurre · 2009-05-07 00:18:20

correct mathsy

hints

Last edited by Kurre (2009-05-07 00:20:42)

JaneFairfax · 2009-05-07 04:16:44

mathsyperson · 2009-05-07 04:54:14

Kurre · 2009-05-07 06:19:49

nice

Last edited by Kurre (2009-05-07 06:27:15)

JaneFairfax · 2009-05-07 06:27:55

Kurre · 2009-05-07 06:52:51

#10 let f be a function from the natural numbers to the natural numbers satisfying

if n-1>m>0. Find the least possible value of f(2009) and f(2011)

Last edited by Kurre (2009-05-07 06:55:34)

Kurre · 2009-05-07 07:07:40

uhm okey that was much nicer than what I did

Kurre · 2009-05-08 03:18:05

#11 Find all functions from the positive rational numbers to the positive rational numbers satisfying:

Last edited by Kurre (2009-05-08 03:28:36)

Kurre · 2009-05-08 22:15:18

#12
Let n be an integer with m prime factors (not necessarily distinct). suppose d|n and define

where and are the multiplicities for p in the prime factorization for n and d respectively. Show that:

and determine when equality occurs.

Last edited by Kurre (2009-05-08 22:15:34)

bobbym · 2009-05-13 01:33:32

Hi Kurre;

I have been working very hard on your #7. I will continue to work on it, but in case I don't get there after a couple of weeks more. I would very much like to see your method.

Kurre · 2009-05-16 06:12:30

bobbym wrote:
Hi Kurre;

I have been working very hard on your #7. I will continue to work on it, but in case I don't get there after a couple of weeks more. I would very much like to see your method.

Im really glad to hear you are working on it

If you want, I can post my solution.

Kurre · 2009-05-16 06:26:45

#13 Let M be a (p-1)x(p-1) matrix where p is an odd prime number and each row has each element from {1,2,3,...,p-2,p-1} exactly once. Prove that p|det(M)

Last edited by Kurre (2009-05-16 07:13:12)

mathsyperson · 2009-05-16 07:07:22

#13 is false for p=2.

Kurre · 2009-05-16 07:15:43

mathsyperson wrote:
#13 is false for p=2.

true, forgot about that. Fixed!

JaneFairfax · 2009-05-16 17:46:48

can be generalized. For each integer , divides the determinant of a matrix in which each positive integer less than and coprime with appears exactly once in each row and in each column.

Kurre · 2009-05-16 21:15:07

JaneFairfax wrote:
can be generalized. For each integer
,
divides the determinant of a
matrix in which each positive integer less than and coprime with
appears exactly once in each row and in each column.

Yea I realized that when trying to sleep yesterday :p
edit: you dont need exactly once in the columns also

Last edited by Kurre (2009-05-16 21:18:45)

Kurre · 2009-05-17 00:48:54

#14
let

be the n roots of unity. For which n and m does it hold that:
?

bobbym · 2009-05-17 09:05:43

Incomplete answer so everyone else please continue to look

Last edited by bobbym (2009-05-17 09:11:55)

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#1 2009-04-18 21:33:01

Kurre's Exercises

#2 2009-05-05 04:45:12

Re: Kurre's Exercises

#3 2009-05-05 06:50:47

Re: Kurre's Exercises

#4 2009-05-05 08:30:08

Re: Kurre's Exercises

#5 2009-05-05 09:03:26

Re: Kurre's Exercises

#6 2009-05-05 18:50:17

Re: Kurre's Exercises

mathsyperson wrote:

#7 2009-05-05 21:29:08

Re: Kurre's Exercises

#8 2009-05-07 00:18:20

Re: Kurre's Exercises

#9 2009-05-07 04:16:44

Re: Kurre's Exercises

#10 2009-05-07 04:54:14

Re: Kurre's Exercises

#11 2009-05-07 06:19:49

Re: Kurre's Exercises

#12 2009-05-07 06:27:55

Re: Kurre's Exercises

#13 2009-05-07 06:52:51

Re: Kurre's Exercises

#14 2009-05-07 07:07:40

Re: Kurre's Exercises

#15 2009-05-08 03:18:05

Re: Kurre's Exercises

#16 2009-05-08 22:15:18

Re: Kurre's Exercises

#17 2009-05-13 01:33:32

Re: Kurre's Exercises

#18 2009-05-16 06:12:30

Re: Kurre's Exercises

bobbym wrote:

#19 2009-05-16 06:26:45

Re: Kurre's Exercises

#20 2009-05-16 07:07:22

Re: Kurre's Exercises

#21 2009-05-16 07:15:43

Re: Kurre's Exercises

mathsyperson wrote:

#22 2009-05-16 17:46:48

Re: Kurre's Exercises

#23 2009-05-16 21:15:07

Re: Kurre's Exercises

JaneFairfax wrote:

#24 2009-05-17 00:48:54

Re: Kurre's Exercises

#25 2009-05-17 09:05:43

Re: Kurre's Exercises

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