单选题则f'(0)为()
单选题A是n阶矩阵,下列命题中错误的是______
单选题设随机变量X和Y相互独立且在(0,a)上服从均匀分布,则E[min(X,Y)]等于
单选题设X1,X2,…,Xn(n>1)是取自总体X的简单随机样本,且DX=σ2>0,为样本均值,则Xn-与的相关系数为A.-1.B.0.C.D.
单选题有完全民事行为能力的人在被宣告死亡期间实施的民事法律行为( )。 A.有效 B.无效 C.部分有效 D.在撤销死亡告后有效
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单选题3阶矩阵A的特征值是0,-1,1.则下列结论不正确的是______
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单选题设lnxn≤lna≤lnyn(n=1,2,…),且.其中a是常数,则与A.都存在且都等于a.B.都存在且都等于1.C.都不存在.D.可能存在,可能不存在.
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单选题设(X,Y)为二维随机变量,则X与Y独立的充要条件为
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单选题设n维向量α
1
,α
2
,…,α
s
的秩为r,则下列命题正确的是
(A) α
1
,α
2
,…,α
s
中任何r-1个向量必线性无关.
(B) α
1
,α
2
,…,α
s
中任何r个向量必线性无关.
(C) 如果s>n,则α
s
必可由α
1
,α
2
,…,α
s-1
线性表示.
(D) 如果r=n,则任何n维向量必可由α
1
,α
2
,…,α
s
线性表示.
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单选题下列各组矩阵相似的是______.A.B.C.D.
单选题The modern university is the ideal environment for the creation and transfer of knowledge that drives national competitiveness in an increasingly global era. Its most effective form is the American adaptation of the European model, in which teaching, leaning and research are integrated into a single institution. Indeed, the American university has proved capable of almost anything, from developing advanced economic theories to creating new life forms. Many national leaders understand that the university is the critical catalyst for America's adaptability, economic robustness and emergence as a great power. And they are moving aggressively to catch up. The universities created by emerging economies beginning in the 1990s and through 2020 will likely play a decisive role in reshaping the global balance of economic power. That is bad news for the United States. The past two decades of American university development have been characterized largely by self-satisfaction arising from steady progress by the top 20 or so research universities. And America as a nation has 1Seen coasting. Since 2000, the United States has lost its edge in the graduation of engineers and technologists. The country no longer dominates scientific discovery, innovation or exploration. Most important, the United States has not launched any effort to build new institutions to accommodate its increasingly diverse population of more than 300 million. The result is that America's university system, despite its historical pre-eminence, has ceased to grow. Furthermore, America's university system has failed to adapt to the dramatic demographic shifts occurring as a result of social mobility and immigration. America needs to realize that its universities face real competition from the rest of the world to attract the best and the brightest, to secure resources and to provide environments that educate and inspire. This is not to say that the best American universities are no longer the leaders in discovery and innovation. It is to say that the success of the higher-education system must be measured by more than just innovations. Its long-term performance depends on its ability to provide learning to a broad cross sections of citizens, to advance national proficiency in math and science and to create an adaptable work force, as well as to develop a national appreciation for discovery, entrepreneurship and the creative process. In China and elsewhere, these are the goals of the new universities being built. In the United States, we need to move from a national self-confidence based on past success to one built on the knowledge that we are advancing a system of higher education that will meet our future needs. This will require that policymakers, business leaders and universities rededicate themselves to creating comprehensive learning and discovery environments; design entirely new models and methods for teaching, and then take action to implement them.
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单选题设f(x)在x=a的某邻域内连续,且f(a)为其极小值.则存在δ>0,当x∈(a-δ,a+δ)且x≠a时,A..B..C..D..