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Unformatted text preview: Ring (R, +, ． ) (2 binary operations): (R, +) is an abelian group ． is associative + ． is distributive (left & right) a ． 1 = 1 ． a = a Ring with unity Commutative Ring No zerodivisors a ． b = b ． a 1 ≠ 0 except the zero ring {0} (R*, ． ) is a group Division Ring Integral Domain (R*, ． ) is an abelian group Field Summands notation in Rings Given an element ‘a’ in ring R : • n ． a = a+a+…+a (n of them) when n>0 • 0 ． a = 0 in R, when n = integer zero • n ． a = (a) + …+ (a) (n of them) when n<0 Basic identities Additive identity 0 in R, any a, b in R : 1. 0a = a0 = 0 2. a(b) = (a)b = (ab) (note the order of ab) 3. (a)(b) = ab 4. (n ． 1) (m ． 1) = (nm) ． 1 Ring Homomorphism & Isomorphism • φ : R → R’ is a homo if for any a, b in R 1. φ (a+b) = φ (a)+’ φ (b) 2. φ (ab) = φ (a) φ (b) (Ring homo implies Group homo) • φ : R → R’ is a isomo if 1. φ is homo 2. φ is 11 & onto Basic homomorphism theorem φ : R → R’ is a homo, (...
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This note was uploaded on 10/13/2010 for the course MATHEMATIC 223H taught by Professor Huang during the Spring '10 term at National Taiwan University.
 Spring '10
 Huang
 Algebra

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