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}