1 and (A-B)∨( A-C)=, what are the necessary and sufficient conditions? (? Can't do it because the topic is incomplete? )。
A、A？ B∪CB、A？ B∪CC、A？ B∩CD、A？ B∩C
Second, fill in the blanks (2 points for each blank, *** 14 points), for example:
1, let the set S={a, b}, and P(S) represents the power set of s, then the Ducal product.
s？ P(S)=？ {aX empty，bX empty，ax {a}，bx {a}，ax {b}，bx {b}，ax {a，b}，bx {a，b}}。
2.f:Z is known? r，f(x)=ex，g:Z？ z，g(x)=x2，A=N，B={2x|x？ N}，
Where R is a real number set, Z is an integer set and N is a natural number set, then
f？ g(A)={}，f？ g(B)={？ }。
3. Let n be natural number set (including 0) and the function f:? N→N？ n，f(n)= & lt； n，n+ 1 & gt； ,
then what f？ The nature of B.
A, not alone, but all the way? B, it's a single shot, not a full shot.
C, is it a double shot? D, not a shot, not a complete shot.
4.n is a set of natural numbers, and the radix of n nns is C.
Where n is an arbitrary positive integer and Nn represents the cartesian product of n n.
5. It is known that graph G has n nodes and m edges, and the degree of each node is either k or k+ 1, then graph G has.
_? nk+n-2m？ _? K-degree node, 2m-nk k+ 1 degree node.
Iii. Calculation questions (3 questions, *** 14), such as:
1, (6 points)? Let X={a, b, c}
( 1)? Do all the divisions of x
Partition 1={{a}, {b}, {c}}, partition 2={{a, b}, {c}}, partition 3={{a}, {b, c}}, partition 4={{a, c}, {b}.
(2)? Let the set formed by all divisions of x be p, and "division" is a partial order relation on p,
Painting? & ltp, segmentation >? Hastu
(3)? Find the maximum element, minimum element, upper bound and lower bound.
Maximum element, upper limit: Part 5
Minimum element, lower limit: partition 1