Problem 1
Use the precise definitions, state all hypotheses, apply (A∪B)^c=A^c∩B^c, and verify the conclusion against a boundary case or independent theorem.
Faculty solution guide
Set Operations and De Morgan Laws
Accept equivalent mathematically correct reasoning. Require explicit definitions, theorem hypotheses, proof structure, verification, and limitations.
Problem 2
Identify the first invalid inference, missing hypothesis, quantifier error, unjustified limit interchange, or unproved existence claim; then supply a valid repair.
Problem 3
A complete response explicitly states the definitions, domain, hypotheses, exact target, and theorem dependencies for Set Operations and De Morgan Laws.
Problem 4
The argument must address proving identities involving unions, intersections, complements, and differences with each nontrivial step justified and the final conclusion restated.
Problem 5
A strong application explains the mathematical model in algebraic structures, analysis, topology, computer science, databases, and mathematical modelling, verifies conditions, and names at least one limitation.
Problem 6
Accept a second valid proof, a counterexample showing necessity of a hypothesis, an independent estimate, or a reproducible finite check that is correctly described as supporting evidence.