MOOC University of Electronic Science and Technology Discrete Mathematics Set Theory First Assignment Answers

1.1 {6, 28, 496}

1.2 {1, 2, 3, 4, 6, 9, 12, 18}

 

2.1 {x|x=5k+2,k∈Z}

2.2 {x|x^2-9x-36>0}

 

3. P(A) = {∅, a, {b}, b, {a, {b}}, {a, b}, { {b}, b}, {a, {b}, b} }

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4. For ∀x, ∃x∈(A - B) - C,

∴ x∈(AB) and x∉C

∴ x∈A and x∉B and x∉C

∴ x∈(AC) and x∉(BC)

∴x∈(A-C)-(B-C)

∴(A-B)-C = (A-C)-(B-C)