December 9th, 2009, 06:04 AM  #1 
Member Joined: Oct 2009 Posts: 85 Thanks: 0  Ideal
Let A and B be ideals of a ring R. Prove that (a) is an ideal of R (b) is an ideal of R 
December 9th, 2009, 06:25 AM  #2 
Senior Member Joined: Oct 2007 From: Chicago Posts: 1,701 Thanks: 3  Re: Ideal
Check what happens if you multiply r (an arbitrary ring element) by an element of or an element of A+B.

December 12th, 2009, 06:46 AM  #3 
Member Joined: Oct 2009 Posts: 85 Thanks: 0  Re: Ideal
Ok for part a) i need to show using and . Proof: let and , . How do i go form here to show that and ? 
December 12th, 2009, 01:11 PM  #4  
Newbie Joined: Jul 2009 Posts: 18 Thanks: 0  Re: Ideal Quote:
 

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