Chapter 11: Problem 1
List all the partitions of the set \(A=\\{a, b\\}\). Compare your answer to the answer to Exercise 5 of Section 11.3 .
Chapter 11: Problem 1
List all the partitions of the set \(A=\\{a, b\\}\). Compare your answer to the answer to Exercise 5 of Section 11.3 .
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Get started for freeModifying Exercise 8 (above) slightly, define a relation \(\sim\) on \(\mathbb{Z}\) as \(x \sim y\) if and only if \(|x-y| \leq 1 .\) Say whether \(\sim\) is reflexive. Is it symmetric? Transitive?
Suppose \(R\) is a reflexive and symmetric relation on a finite set \(A .\) Define a relation \(S\) on \(A\) by declaring \(x S y\) if and only if for some \(n \in \mathbb{N}\) there are elements \(x_{1}, x_{2}, \ldots, x_{n} \in A\) satisfying \(x R x_{1}, x_{1} R x_{2}, x_{2} R x_{3}, x_{3} R x_{4}, \ldots, x_{n-1} R x_{n},\) and \(x_{n} R y .\) Show that \(S\) is an equivalence relation and \(R \subseteq S .\) Prove that \(S\) is the unique smallest equivalence relation on \(A\) containing \(R\).
Let \(A=\\{a, b, c, d\\} .\) Suppose \(R\) is the relation $$ \begin{aligned} R=&\\{(a, a),(b, b),(c, c),(d, d),(a, b),(b, a),(a, c),(c, a)\\\ &(a, d),(d, a),(b, c),(c, b),(b, d),(d, b),(c, d),(d, c)\\} \end{aligned} $$ Is \(R\) reflexive? Symmetric? Transitive? If a property does not hold, say why.
Let \(A=\\{a, b, c, d, e\\} .\) Suppose \(R\) is an equivalence relation on \(A .\) Suppose \(R\) has two equivalence classes. Also \(a R d, b R c\) and \(e R d\). Write out \(R\) as a set.
Describe the partition of \(\mathbb{Z}\) resulting from the equivalence relation \(\equiv(\bmod 4)\)
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