8.一次抛掷两枚骰子,向上点数之和不小于10的概率为( )
| A. | $\frac{1}{6}$ | B. | $\frac{1}{9}$ | C. | $\frac{2}{9}$ | D. | $\frac{1}{4}$ |
5.圆C:x2+y2-4x+2y=0的圆心坐标和半径分别为( )
| A. | C(2,1),r=5 | B. | C(2,-1),r=$\sqrt{5}$ | C. | C(2,-1),r=5 | D. | C(-2,1),r=$\sqrt{5}$ |
4.已知等差数列{an}中,a4+a6=8,则a3+a4+a5+a6+a7=( )
| A. | 10 | B. | 16 | C. | 20 | D. | 24 |
3.已知集合A={1,2,3,4},B={x|x2-3<0},则A∩B=( )
| A. | {1} | B. | {1,2} | C. | {1,2,3} | D. | {1,2,3,4} |
20.从1,2,3,…,9这九个整数中同时取四个不同的数,其和为偶数,则不同取法共有( )
0 240705 240713 240719 240723 240729 240731 240735 240741 240743 240749 240755 240759 240761 240765 240771 240773 240779 240783 240785 240789 240791 240795 240797 240799 240800 240801 240803 240804 240805 240807 240809 240813 240815 240819 240821 240825 240831 240833 240839 240843 240845 240849 240855 240861 240863 240869 240873 240875 240881 240885 240891 240899 266669
| A. | 62 | B. | 64 | C. | 65 | D. | 66 |