4.下列运算正确的是( )
| A. | x2•x3=x6 | B. | x6÷x5=x | C. | (-x2)4=x6 | D. | x2+x3=x5 |
3.-$\frac{1}{5}$的倒数是( )
| A. | -$\frac{1}{5}$ | B. | $\frac{1}{5}$ | C. | -5 | D. | 5 |
2.下列说法中,正确的是( )
0 307859 307867 307873 307877 307883 307885 307889 307895 307897 307903 307909 307913 307915 307919 307925 307927 307933 307937 307939 307943 307945 307949 307951 307953 307954 307955 307957 307958 307959 307961 307963 307967 307969 307973 307975 307979 307985 307987 307993 307997 307999 308003 308009 308015 308017 308023 308027 308029 308035 308039 308045 308053 366461
| A. | 同一条弦所对的两条弧一定是等弧 | |
| B. | 长度相等的两条弧是等弧 | |
| C. | 两条直线被一组平行线所截,所得的对应线段成比例 | |
| D. | 三角形的外心到三角形各边的距离相等 |