University of California, San Diego: Edward Bender and S. Williamson's "Sets, Equivalence and Order: Sets and Functions"

Study pages SF-1 and SF-2, and Theorem 1 on pages SF-2 and SF-3. The set difference laws: A - (B U C) = (A - B) ∩ (A - C);  A - (B ∩ C) = (A - B) U (A - C) follow from the definition of set difference and De Morgan's Laws (use the fact the A - B = A ∩ B').

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