Let a,b,c,and d be real number with |a-b|=2 b-c=3 c-d=4 .What is the sum of all possible values of a-d? 答案为一个数答案为18 我也不明白 a减d

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 you and _____good friends.A.I am B.me be C.me are D.I are(选择 Let R be the relation on Z×Z ,that is elements of this relation arepairs of pairs of integers,such that ((a,b),(c,d)) ∈ R if and only ifa+d = b+c.Is R an equivalence relation?Explain. A circle is inscribed in a triangle with sides of lengths of 8,17,and 19.Let the segments determined by the point of tangency on the side of length 8 be w and r,with w < r.Find the ratio of w to r.a) 3:5b) 5:7 c) 2:3 d) 1:5 e) 7:9麻烦另付翻译 Let us ____good friends and always help each other.A.to be B.are C.be D.get回答写理由快 Let us -----good friends,shall we?A to be B be C are D being 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 ( )friends.A I am B I are Cme are D me be 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 The book is borrowed from the library .You ___your children put dots andlines here and there.A.shouldn’t be letting B.needn’t have let C.ought not to have let to D.mustn’t have let为什么 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 英语翻译Once the actor Edwards told his fans,Be yourself and don't let anybody ------- you around.a.pull b.push c.take d.turn The salesman scolded the girl caught ____ and let her off.A.to have stolen B.to be stealing C.to steal D.stealingWhy Meaning? Let you and_____good friends.And let_____help you.A.my are;I B.I am;I C.me be;me d.I are;me(选择并说明） Dinner will be ready _______.Let’s go and wash our hands.A) at all B) at least C) just now D) right away 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=