11.若变量x,y满足约束条件$\left\{\begin{array}{l}y≤2x\\ x+y≥1\\ y≥-1\end{array}\right.$,则x+2y的最小值是( )
| A. | $-\frac{5}{2}$ | B. | 0 | C. | $\frac{5}{3}$ | D. | $\frac{5}{2}$ |
10.设i是虚数单位,复数$z=\frac{{{i^5}(2+i)}}{2-i}$,其共轭复数$\overline z$的虚部是( )
| A. | $\frac{3}{5}$ | B. | $\frac{3}{5}i$ | C. | -$\frac{3}{5}$ | D. | $-\frac{3}{5}i$ |
5.设x3+ax+b=0,其中a,b均为实数.下列条件中不能使得该三次方程仅有一个实根的是( )
| A. | a=-3,b=~3 | B. | a=0,b=2 | C. | a=-3,b=2 | D. | a=1 b=2 |
4.命题“?n0∈N*,f(n)∈N*且f(n0)>n0的否定形式为( )
0 226674 226682 226688 226692 226698 226700 226704 226710 226712 226718 226724 226728 226730 226734 226740 226742 226748 226752 226754 226758 226760 226764 226766 226768 226769 226770 226772 226773 226774 226776 226778 226782 226784 226788 226790 226794 226800 226802 226808 226812 226814 226818 226824 226830 226832 226838 226842 226844 226850 226854 226860 226868 266669
| A. | ?n∈N*,f(n)∉N*或f(n)≤n | B. | ?n∈N*,f(n)∉N*且f(n)>n | ||
| C. | ?n0∈N*,f(n0)∉N*且f(n0)>n0 | D. | ?n∈N*,f(n)∉N*且f(n)>n |