17.下列计算中,正确的是( )
| A. | 2a(3a-1)=6a3-1 | B. | x•x3=x3 | C. | (-2xy2)4=16x4y8 | D. | x3+x3=x6 |
13.若代数式$\frac{\sqrt{x+1}}{(x+3)^{2}}$有意义,则实数x的取值范围是( )
| A. | x≥-1且x≠-3 | B. | x≥-1 | C. | x>-1 | D. | x>-1且x≠3 |
12.已知三角形三条边的长度分别是:①1,$\sqrt{2}$,$\sqrt{3}$;②2,3,4;③3n,4n,5n(n>0);④32,42,52.其中一定能构成直角三角形的有( )
| A. | 1组 | B. | 2组 | C. | 3组 | D. | 4组 |
9.在下列四个图案中是轴对称图形的是( )
0 284858 284866 284872 284876 284882 284884 284888 284894 284896 284902 284908 284912 284914 284918 284924 284926 284932 284936 284938 284942 284944 284948 284950 284952 284953 284954 284956 284957 284958 284960 284962 284966 284968 284972 284974 284978 284984 284986 284992 284996 284998 285002 285008 285014 285016 285022 285026 285028 285034 285038 285044 285052 366461
| A. | B. | C. | D. |