Math Help Forum

Math Help Forum Feed Site Feed

Go Back   Math Help Forum > Math Help Forum Lounge > Problem of the Week
Reply
 
Thread Tools Display Modes
  #1  
Old 02-24-2008, 02:56 PM
ThePerfectHacker's Avatar
Global Moderator

 
Join Date: Nov 2005
Location: New York City
Posts: 11,339
Country:
Thanks: 329
Thanked 2,943 Times in 2,472 Posts
ThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond repute
Default Problem 46

1)Let f(x) be a monic polynomial* with integer coefficients with \deg f(x) \geq 1. Prove that if the sum of all coefficients and the product of all the complex zeros (counting multiplicity) are both odd then the polynomial has not integer zeros.

*)Leading term is 1.
__________________
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

Last edited by ThePerfectHacker; 02-28-2008 at 09:29 PM.
Reply With Quote
The following users thank ThePerfectHacker for this useful post:
Donate to MHF
Advertisement
 
  #2  
Old 02-28-2008, 06:52 AM
JaneBennet's Avatar
Senior Member
 
Join Date: Dec 2007
Posts: 249
Country:
Thanks: 51
Thanked 251 Times in 154 Posts
JaneBennet is a jewel in the roughJaneBennet is a jewel in the roughJaneBennet is a jewel in the roughJaneBennet is a jewel in the rough
Default

By “complex zeros”, do you mean both complex and real zeros, or just complex non-real zeros?
Reply With Quote
The following users thank JaneBennet for this useful post:
Donate to MHF
  #3  
Old 02-28-2008, 08:21 AM
ThePerfectHacker's Avatar
Global Moderator

 
Join Date: Nov 2005
Location: New York City
Posts: 11,339
Country:
Thanks: 329
Thanked 2,943 Times in 2,472 Posts
ThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond repute
Default

Quote:
Originally Posted by JaneBennet View Post
By “complex zeros”, do you mean both complex and real zeros, or just complex non-real zeros?
I mean all zeros. For example, take x^3+x then the zeros are 0,i,-i. Does saying "zeros in \mathbb{C}" make it better?
__________________
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
Reply With Quote
The following users thank ThePerfectHacker for this useful post:
Donate to MHF
  #4  
Old 02-28-2008, 04:57 PM
Henderson's Avatar
Senior Member
 
Join Date: Dec 2007
Posts: 104
Country:
Thanks: 5
Thanked 36 Times in 33 Posts
Henderson is on a distinguished road
Default

I must not understand the question. My first thought is:
f(x) = (x-1)(x-3)(x-5) = x^3 - 9x^2 +23x - 15.

The sum of the zeros is 9, the product of the zeros is 15, and all three zeros are integers.
Reply With Quote
The following users thank Henderson for this useful post:
Donate to MHF
  #5  
Old 02-28-2008, 09:28 PM
ThePerfectHacker's Avatar
Global Moderator

 
Join Date: Nov 2005
Location: New York City
Posts: 11,339
Country:
Thanks: 329
Thanked 2,943 Times in 2,472 Posts
ThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond reputeThePerfectHacker has a reputation beyond repute
Default

Thank you. I was inventing this problem, I should have been more careful. I fixed it above. Tell me if it is okay now.
__________________
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
Reply With Quote
The following users thank ThePerfectHacker for this useful post:
Donate to MHF
  #6  
Old 10-20-2008, 04:45 PM
Member
 
Join Date: Oct 2008
Location: Guernsey
Posts: 25
Country:
Thanks: 0
Thanked 10 Times in 10 Posts
SimonM is on a distinguished road
Send a message via AIM to SimonM Send a message via MSN to SimonM
Default

By considering the equation \pmod{2} and the fact that f(1) and f(0) are both odd implies the truth of your statement
Reply With Quote
Reply
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off
Forum Jump


All times are GMT -7. The time now is 09:05 AM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2008, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.2.0 ©2008, Crawlability, Inc.
©2005 - 2008 Math Help Forum


Math Help Forum is a community of maths forums with an emphasis on maths help in all levels of mathematics.
Register to post your math questions or just hang out and try some of our math games or visit the arcade.