Math Problem Statement

Suppose ρ is a relation defined on the set Z, ρ = {(x, y) ∈ Z × Z | x divides y}. Then ρ is: (A) Reflexive (B) Symmetric (C) Both A and B (D) None of these

Solution

The problem asks us to analyze the relation ρ\rho defined on the set Z\mathbb{Z} (the set of integers), where ρ={(x,y)Z×Z  x divides y}\rho = \{(x, y) \in \mathbb{Z} \times \mathbb{Z} \ | \ x \text{ divides } y\}. We need to determine the properties of this relation—whether it is reflexive, symmetric, or both.


Analysis

  1. Reflexivity: A relation is reflexive if for every xZx \in \mathbb{Z}, (x,x)ρ(x, x) \in \rho.

    • For any integer xx, xx divides xx (since x/x=1x/x = 1, which is an integer).
    • Hence, ρ\rho is reflexive.
  2. Symmetry: A relation is symmetric if (x,y)ρ(x, y) \in \rho implies (y,x)ρ(y, x) \in \rho.

    • If xx divides yy, it does not necessarily follow that yy divides xx. For example, 262 \mid 6, but 626 \nmid 2.
    • Hence, ρ\rho is not symmetric.
  3. Conclusion: Since ρ\rho is reflexive but not symmetric, the correct answer is:

(A) Reflexive


Would you like further clarification or a breakdown of the definitions? Here are related questions to expand your understanding:

  1. What is the definition of transitivity in relations, and is ρ\rho transitive?
  2. How can we test if a relation is symmetric using specific examples?
  3. What are some common relations on Z\mathbb{Z} that are both reflexive and symmetric?
  4. How does divisibility differ from equality in determining reflexivity or symmetry?
  5. Could you extend the concept of divisibility to modular arithmetic relations?

Tip: To quickly check symmetry, use counterexamples involving non-equal integers.

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Math Problem Analysis

Mathematical Concepts

Set Theory
Relations
Divisibility
Properties of Relations (Reflexivity, Symmetry)

Formulas

Definition of divisibility: x divides y if ∃k ∈ Z such that y = kx

Theorems

Properties of Relations: Reflexivity, Symmetry, and Transitivity

Suitable Grade Level

Undergraduate or Advanced High School (Grades 11-12)