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Discrete mathematics set theory
1- 1 Let the set A ={ 1, {2}, a, 4, 3}, and the following proposition is true [B].

A . 2∈A; b . 1∈A; c . 5∈A; {2} Answer.

If 1-2 A and b are arbitrary sets, then their * * * isomorphic subset is [D].

A.a; B . Bc . A∪B; d? .

1-3 let S = {N, z, q, R}, and judge whether the following proposition holds?

(1) N is included in q, Q ∈S, then n is included in (or belongs to) s [No].

(2)- 1 ∈Z, Z ∈S, then-1∈S[ No]

1-4 Let the sets a = {3 3,4} and B = {4,4} ∩? ,C = {4,3} ∩{? },D ={ 3,4,? },

E = {x│x ∈R and x2-7x+ 12 = 0}, F = {4,? ,3,3},

Which two groups can be represented by equal signs? A=E,F=D,B=C

1-5 The following sets are represented by column element method.

(1)A = {x│x ∈N and x2 ≤ 9} = {1, 2,3}

(2)A = {x│x ∈N and 3-x < 3} = {1, 2}