已选分类
理学数学
单选题设，其中c1，c2，c3，c4为任意常数，则下列向量组线性相关的为______。A.α1，α2，α3B.α1，α2，α4C.α1，α3，α4D.α2，α3，α4
单选题设k＞0，函数在(0，+∞)内零点的个数为______．A．3B．2C．1D．0
单选题一个圆柱体的高减少到原来的70%，底半径增加到原来的130%，则它的体积( )． A．不变 B．增加到原来的121% C．增加到原来的130% D．增加到原来的118.3% E．减少到原来的91%
单选题
单选题A survey of 100 persons revealed that 72 of them had eaten at restaurant P and that 52 of them had eaten at restaurant Q. Which of the following could not be the number of persons in the surveyed group who had eaten at both P and Q?
单选题If the width of a rectangle is increased by 25% while the length remains constant, the resulting area is what percent of the original area?
单选题设A，B都是n阶方阵，齐次线性方程组Ax=0与Bx=0有相同的基础解系ξ1，ξ2，ξ3，则ξ1，ξ2，ξ3也是下列方程组的基础解系______。A．(A+B)x=0B．ABx=0C．D．以上都不对
单选题若函数，则=______。A.x=0B.x=1C.x=-1D.不存在
单选题
单选题某个数列的通项公式为an+2=an+an+1(n≥1)，问a6=? (1)a6-a5=3 (2)a7+a8=34
单选题
单选题问下列哪个点(r，s)在直线y=2x+3上? (1)(2r-s+3)(4r+2s-6)=0 (2)(3r+2s-5)(2r-s+3)=0
单选题
单选题
单选题设向量组Ⅰ：α1，α2，…，αm，其秩为r；向量组Ⅱ：α1，α2，…，αm，β，其秩为s。则r=s是向量组Ⅰ与向量组Ⅱ等价的______
A.充分非必要条件
B.必要非充分条件
C.充分必要条件
D.既非充分也非必要条件
单选题问N为多少? (1)N只有2和3两个质因子 (2)N的因子个数为12。
单选题设α1，α2，α3为3维列向量，矩阵A=(α1，α2，α3)，B=(α2，2α1+α2，α3)。若行列式|A|=3，则行列式|B|=______。
A.6
B.3
C.-3
D.-6
单选题x+y为整数，y为整数吗? (1)x-y为整数； (2)x+2y为整数。
单选题
单选题A department store receives a shipment of 1,000 shirts, for which it pays $9,000. The store sells the shirts at a price 80 percent above cost for one month, after which it reduces the price of the shirts to 20 percent above cost. The store sells 75 percent of the shirts during the first month and 50 percent of the remaining shirts afterward. How much gross income did sales of the shirts generate? (A) $10,o00 (B) $10,800 (C) $12,150 (D) $13,500 (E) $16,200