问答题对一切实数t，函数f(t)是连续的正函数，又f(-t)=f(t)，函数

问答题已知X服从参数为1的指数分布，Y=|X|，试求： (Ⅰ)(X，Y)的分布函数F(x，y)； (Ⅱ)关于X和关于Y的边缘分布函数Fx(x)和Fy(y)； (Ⅲ)X，Y的相关系数ρXY．

问答题Almost all our major problems involve human behavior, and they cannot be solved by physical and biological technology alone. What is needed is a technology of behavior, but we have been slow to develop the science from which such a technology might be drawn, (46) One difficulty is that almost all of what is called behavioral science continues to trace behavior to states of mind, feelings, traits of character, human nature, and so on. Physics and biology once followed similar practices and advanced only when they discarded them, (47) The behavioral sciences have been slow to change partly because the explanatory items often seem to be directly observed and partly because other lands of explanations have been hard to find. The environment is obviously important, but its role has remained obscure. It does not push or pull, it selects, and this function is difficult to discover and analyze. (48). The role of natural selection in evolution was formulated only a little more than a hundred years ago, and the selective role of the environment in shaping and maintaining the behavior of the individual is only beginning to be recognized and studied. As the interaction between organism and environment has come to be understood, however, effects once assigned to states of mind, feelings, and traits are beginning to be traced to accessible conditions, and a technology of behavior may therefore become available. It will not solve our problems, however, until it replaces traditional pre-scientific views, and these are strongly entrenched. Freedom and dignity illustrate the difficulty. (49) They are the possessions of the autonomous (self-governing) man of traditional theory, and they are essential to practices in which a person is held responsible for his conduct and given credit for his achievements. A scientific analysis shifts both the responsibility and the achievement to the environment. It also raises questions concerning "values". Who will use a technology and to what ends? (50) Until these issues are resolved, a technology of behavior will continue to be rejected, and with impossibly the only way to solve our problems.

问答题设二维随机变量(X，Y)的联合密度为

问答题求函数f(x，y，z)=2x+2y+x2+y2-z2在Ω：x2+y2+z2≤1上的最大值与最小值．

问答题设随机变量X与Y相互独立同分布，其中令U=max(X，Y)，V=min(X，Y)．1.求(U，V)的联合分布；

问答题设(2E-C-1B)AT，其中E是4阶单位矩阵，AT是4阶单位矩阵A的转置矩阵，且求矩阵A．

问答题设求a，b及正交矩阵P，使得PTAP=B．

问答题设计算其中D：|x|+|y|≤2.

问答题计算I=(x+3z2)dydz+(x3z2+yz)dzdx-3y2dxdy，其中∑为在z=0上方部分的下侧．

问答题设区域，分别求D绕x轴和y轴旋转一周而成的旋转体体积Vx与Vy．