Exercise 17.3.3. Show that each of these binary relations is an equivalence relation. (a) The binary relation~ on R defined by r ~y iff r² - 3x = y² − 3y. (b) The binary relation ~ on R defined by r ~ y iff r − y € Z. (*Hint*) (c) The binary relation ~ on Nx N defined by (a1, b₁) ~ (a2, b2) iff a1b2 = a2b1. (*Hint*) (d) The binary relation on C defined by 21 ~ 22 iff |21| = |22|- Equivalence relations are often defined in terms of functions. For in- stance, Example 17.3.1 involves the function f: R→ R defined by f(x) = 2², and ~ y if and only if f(x) = f(y). Similarly, Exercise 17.3.3 involves the function g: R → R defined by f(x)=x²-3x, and r ~ y if and only if g(x) = g(y). Both of these cases follow the following pattern: Given a function f : A → B, define a binary relation on A by: a₁ ~ az iff f(a₁) Other examples that we've seen also follow this same pattern: Exercise 17.3.4. Following the pattern that we've shown for Example 17.3.1 and Exercise 17.3.3, define the following equivalence relations in terms of functions. (a) Exercise 17.3.3 part (d)
Exercise 17.3.3. Show that each of these binary relations is an equivalence relation. (a) The binary relation~ on R defined by r ~y iff r² - 3x = y² − 3y. (b) The binary relation ~ on R defined by r ~ y iff r − y € Z. (*Hint*) (c) The binary relation ~ on Nx N defined by (a1, b₁) ~ (a2, b2) iff a1b2 = a2b1. (*Hint*) (d) The binary relation on C defined by 21 ~ 22 iff |21| = |22|- Equivalence relations are often defined in terms of functions. For in- stance, Example 17.3.1 involves the function f: R→ R defined by f(x) = 2², and ~ y if and only if f(x) = f(y). Similarly, Exercise 17.3.3 involves the function g: R → R defined by f(x)=x²-3x, and r ~ y if and only if g(x) = g(y). Both of these cases follow the following pattern: Given a function f : A → B, define a binary relation on A by: a₁ ~ az iff f(a₁) Other examples that we've seen also follow this same pattern: Exercise 17.3.4. Following the pattern that we've shown for Example 17.3.1 and Exercise 17.3.3, define the following equivalence relations in terms of functions. (a) Exercise 17.3.3 part (d)
Elements Of Modern Algebra
8th Edition
ISBN:9781285463230
Author:Gilbert, Linda, Jimmie
Publisher:Gilbert, Linda, Jimmie
Chapter1: Fundamentals
Section1.7: Relations
Problem 11E: Let be a relation defined on the set of all integers by if and only if sum of and is odd. Decide...
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