Abstract Algebra: Theory and Applications · Problem 1.26

Preliminaries — Thomas Judson

Mathematics — Abstract Algebra · set-theory-cardinality

Problem

Let

U

be a set with subsets

A

and

B

. ((a)) Prove

A \subset B

if and only if

A \cap B = A

. ((b)) Prove

A \cup B = B

if and only if

A \subset B