已选分类
理学数学
单选题下列乘积中( )是四阶行列式D中前面取负号的项． (a)a13a24a32a11 (b)a12a23a34a43 (c)a11a22a34a43 (d)a14a23a32a41
单选题设随机变量X服从(-1，1)上的均匀分布，事件A={0＜X＜1}，B={X||＜}，则______。A.P(AB)=0B.P(AB)=P(A)C.P(A)+P(B)=1D.P(AB)=P(A)·P(B)
单选题已知f(xy，x+y)=x3+y3，则等于______
单选题坐标平面上直线l向z轴正方向平移3个单位长度，再向Y轴负方向平移5个单位长度，则它和原来的直线l重合，那么l的斜率是()．
单选题如图所示，在平行四边形ABCD中，∠ABC的平分线交AD于E，∠BED=150°，则∠A的大小为______．
单选题函数y=x2-x+1在区间[-1，3]上满足拉格朗日中值定理的ξ等于______．A．B．0C．D．1
单选题对于微分方程y"-2y"+y=xe
x
，利用待定系数法求其特解y
*
时，下列特解设法正确的是______．
单选题某公司有9名工程师，张三是其中之一，从中任意抽调4人组成攻关小组，包括张三的概率是______．A．B．C．D．E．
单选题设η
1
，η
2
，η
3
，η
4
是齐次线性方程组Ax=0的基础解系，则Ax=0的基础解系还可以是
单选题
单选题下列说法正确的是A．或A，B为对立事件，则B．若P(AB)=0，则P(A)=0或P(B)=0C．若A与B互不相容，则P(A)=1-P(B)D．若A与B互斥，则
单选题|3x+2|+2x2-12xy+18y2=0，则2y-3x=______．A．B．C．0D．E．
单选题已知等腰直角三角形ABC和等边三角形BDC(如图18-1)，设△ABC的周长为，则△BDC的面积是( )．
单选题设f(x)=ln2+e3，则f"(x)=______A．B．0C．ln2+e3D．(ln2+3e2)
单选题若(am+1．bn+2)．(a2n-1．b2m)=a5b3，则m+n的值为( )。 A．1 B．2 C．3 D．-3
单选题设____
单选题同宿舍的4名MBA研究生中，至少有两人的生日在同一个月的概率为()．
单选题设集合则A∩B的元素个数为()．
单选题Are teens and young adults more narcissistic (自恋的) today than in the past? That's the view of a California researcher who studies (1) people. In her new book, The Narcissism (2) : Living in the Age of Entitlement, psychologist Jean Twenge of San Diego State University and (3) W. Keith Campbell of the University of Georgia say research shows (4) young people today have "narcissistic traits" than in (5) generations. Such traits, Twenge says, include a very. (6) and inflated sense of self, which is (7) by a preoccupation with MySpace, Facebook and YouTube. "We've been on this self-admiration cultural (8) for a long time," Twenge says. (9) Twenge's take on today's young people isn't universal. Studies by other researchers, including Canadian (10) Dr. Kali of the University of Western Ontario, have used the same data but found (11) results. "They put a different (12) on it," Kali says. Twenge's studies have found more narcissistic traits and a (13) rate of increase among college students today, but Kali found that students' narcissism was (14) greater in 2006 than in 1976. Twenge's most recent paper studied the same data as Kali--more than 20 000 college students from 2002 to 2007. (15) researchers used the Narcissistic Personality Inventory to measure narcissistic (16) and findings by both have been (17) in peerreviewed journals. Twenge's book (18) just a month after The Mirror Effect : How Celebrity Narcissism Is Seducing America, a book co-written by behavioral (19) Drew Pinsky, (20) suggested that a celebrity-obsessed culture is causing more narcissism.
单选题设A，B为n阶矩阵，则下列结论正确的是______．