证明1.Let A,B,and C be sets.Prove thatA∪包含 (A∪B ∪C).2.Let A,B,and C be sets.Prove that(A-C)∩(C -B) = 空集

来源：学生作业帮助网编辑：作业帮时间：2024/05/18 11:11:45

证明1.Let A,B,and C be sets.Prove thatA∪包含 (A∪B ∪C).2.Let A,B,and C be sets.Prove that(A-C)∩(C -B) = 空集
证明
1.Let A,B,and C be sets.Prove that
A∪包含 (A∪B ∪C).
2.Let A,B,and C be sets.Prove that
(A-C)∩(C -B) = 空集

证明1.Let A,B,and C be sets.Prove thatA∪包含 (A∪B ∪C).2.Let A,B,and C be sets.Prove that(A-C)∩(C -B) = 空集
1、
Pick a∈A∪B ,then a a∈A or a∈B.
there are two cases:
case 1 :a∈A,then a must be a member of
one of A,B,C.that means a a∈A∪B ∪C
case 2:a∈B,similarly discuss.
so in both cases,a must be member of A∪B ∪C
that means A∪B is subset of ∪B ∪C
2.Pick a∈(A-C),a must be in A and not in C.because a is not C,a is not in C-B.
so,for every element a ,a can not be in both (A-C) and (B-C).that means (A-C)∩(C -B) has no element.
therefore,(A-C)∩(C -B) is empty set.

1，如果证明A∪B包含 (A∪B ∪C)
任取x属于A∪B
它要么在A中,要么在B中
所以也一定在 (A∪B ∪C)中
所以成立
2，因为(A-C)里的元素是不属于C的，而(C -B) 中的元素都是属于C的
所以它们不相交，所以是空集

证明1.Let A,B,and C be sets.Prove thatA∪包含 (A∪B ∪C).2.Let A,B,and C be sets.Prove that(A-C)∩(C -B) = 空集 Let Ben and Tom ( )good friends.A is B are C be D will be ( )Let john and jack______our friends.A.be B.to be C.are D.is Let me introduce my sister____you.A.to B.for C.and D.be let a,b and c be rational numbers and b=0.24-0.26a,c=0.26-0.24a,then a^2-b^2+c^2= let a,b and c be rational numbers and b=0.24-0.26a,c=0.26-0.24a,then a^2-b^2+c^2= Let a,b and c be ration numbers and b=12/5-13/5a,c=13/5-12/5a.then a2-b2+c2=? 关于凸函数,凹函数的证明题求助!急~~~~~!Let f(x) be a function on R^n. Prove that f is both convex and concave if and only if f(x)=(c^T)x+b for some vector c and scalar b.翻译：f(x)是R^n上一函数.证明f既是凸函数也是凹函数分问题求证明Exercise 8.Suppose on a recent exam,Amy received an A,Joe received a D,Megreceived a B,and Sam received an A.Let R = { Amy,Joe,Meg,Sam }10 1.PREPARATORY MATERIALLet S = {A,B,C,D,F}Let T = {A,B,D}Let f = {(Amy,A),(Joe,D),(Meg,B),( Let you and _____good friends.A.I am B.me be C.me are D.I are(选择 Let is ( )pen friends.A:be B:are C:is Tom,Let,s play__that ball.A.with B./ C.and Let us ____good friends and always help each other.A.to be B.are C.be D.get回答写理由快一.三个互不相等的有理数,即可分别表示为1,a+b,a的形式,又可分别表示为0,a/b,b的形式,则a^2000+b^2001＝?二.Let a be integral part of 根号2 and b be its decimal part.Let c be the integral of π（派） and d be the decim let a,b and c be rational numbers and b=5分之12-5分之13a,c=5分之13-5分之12a,then a的平方-b的平方+c的平方又是一道英语的数学题.let a,b and c be rational numbers and b=12/5-13/5a,c=13/5-12/5a,then a²-b²+c²=—— Supper__ ready and let's go and have___ A.may be,supper B.is,it 7下英语单选1.Let's be _______ and try to be _______ to others.A.friends;friendly B.friendly;friends C.friends;friends D.friendly;friendly