单选题设A，B，A+B，A -1 +B -1 均为n阶可逆矩阵，则(A -1 +B -1 ) -1 等于

单选题设f(x)在x=1的某邻域内连续，且则x=1是f(x)的A.不可导点．B.可导点但不是驻点．C.驻点，且是极大值点．D.驻点，且是极小值点．

单选题设非负函数f(x)满足条件f"(x)≤0，收敛，则______A．B．C．D．

单选题下列定积分的值等于0的是()

单选题已知(X，Y)服从二维正态分布，EX=EY=μ，DX=DY=σ 2 ，X与Y的相关系数ρ≠0，则X与Y

单选题设，则dz=()A．B．C．D．

单选题 设为向量空间的基,的线性变换在此基下的矩阵为，则为单射的充分必要条件是 A、. B、. C、存在,使. D、0是的特征值.

单选题称e -x 是无穷小量是指在下列哪一过程中它是无穷小量______

单选题设f(x)是连续函数，

单选题A.条件(1)充分，但条件(2)不充分。B.条件(2)充分，但条件(1)不充分。C.条件(1)和(2)单独都不充分，但条件(1)和(2)联合起来充分。D.条件(1)充分，条件(2)也充分。E.条件(1)和(2)单独都不充分，条件(1)和条件(2)联合起来也不充分。

单选题设f(x)是以3为周期的可导函数且f"(4)=1，则等于

单选题函数y=ax 2 +b在(-∞，0)内单调增加，则a，b应满足______

单选题若函数在x=0处可导，则a、b之值为()。A．a=0，b=1B．a=1，b=1C．a=2，b=0D．a=1，b=0

单选题It is often observed that the aged spend much time thinking and talking about their past lives, (1) about the future. These reminiscences are not simply random or trivial memories, (2) is their purpose merely to make conversation. The old person's recollections of the past help to (3) an identity that is becoming increasingly fragile: (4) any role that brings respect or any goal that might provide (5) to the future, the individual mentions their past as a reminder to listeners, that here was a life (6) living. (7) , the memories form part of a continuing life (8) , in which the old person (9) the events and experiences of the years gone by and (10) on the overall meaning of his or her own almost completed life. As the life cycle (11) to its close, the aged must also learn to accept the reality of their own impending death. (12) this task is made difficult by the fact that death is almost a (13) subject in the United States. The mere discussion of death is often regarded as (14) As adults many of us find the topic frightening and are (15) to think about it—and certainly not to talk about it (16) the presence of someone who is dying. Death has achieved this taboo (17) only in the modern industrial societies. There seems to be an important reason for our reluctance to (18) the idea of death. It is the very fact that death remains (19) our control; it is almost the only one of the natural processes (20) is so.

单选题设，则a，b，c的大小关系是______．

单选题 设有理系数多项式其中为互不相同的次数大于1的首一不可约有理系数多项式，则在复数域内 A、无重根 B、可能有重根 C、无实根 D、有个实根

单选题设在x=0处连续，且，则a=A．2B．-2C．D．

单选题若α，β是方程x 2 -3x+1=0的两根，则8α 4 +21β 3 =______．

单选题若实数x，y满足条件：x2+y2-4x+1=0，则的最大值是______．A．B．C．D．1E．

单选题已知地球的表面积约等于5.1亿平方公里，其中水面面积约等于陆地面积的倍，则地球上的陆地面积约等于()亿平方公里(精确到0.1亿平方公里)．