对于条件“项目3的实施必须以4的实施为前提条件”,下面描述正确的是:
A: x3=x4=1
B: x3=x4
C: x3≥x4
D: x3≤x4
A: x3=x4=1
B: x3=x4
C: x3≥x4
D: x3≤x4
举一反三
- 设X1,X2,X3,X4是来自总体X的样本,已知总体X~N(0,1),则 A: N(0,1) B: X2(4) C: t(4) D: X2(3)
- X=(x1,x2,x3,x4)T=(0,0,6,4)T是约束条件3x1+2x2+x3=6,2x1+x2+x4=4,x1,x2,x3,x4≥0的一个可行解。()
- 继续上题,为了程序编写简洁,要给数据框x中的6列重新命名为x1,x2,x3,x4,x5,x6,应该使用的命令是() A: ColNames(x) <- c("x1","x2","x3","x4","x5","x6") B: Names(x) <- c("x1","x2","x3","x4","x5","x6") C: colnames(x) <- c("x1","x2","x3","x4","x5","x6") D: colname(x) <- c("x1","x2","x3","x4","x5","x6")
- 【单选题】设全集U={x|-7≤x≤7},A={x|-1≤x4},B={x|-2≤x≤3},Cu(A∪B)= A. {x|-7≤x≤-1} B. {x|-7≤x≤-1或3<x≤7} C. {x|-7≤x<2或4≤x≤7} D. {4≤x≤7}
- 以下程序片段的运行结果是_________。 int x1=30,x2=40; sub(int x,int y) { x1=x; x=y; y=x1; } int main() { int x3=10,x4=20; sub(x3,x4); sub(x2,x1); printf(“%d,%d,%d,%d\n”,x3,x4,x1,x2); }