19.下列运算正确的是( )
| A. | $\sqrt{25}=±5$ | B. | $\root{3}{-8}=-2$ | C. | $\sqrt{12}=3\sqrt{2}$ | D. | $3\sqrt{2}-2\sqrt{2}=1$ |
17.
如图,点A、B、C在⊙O上,CO的延长线交AB于点D,BD=BO,∠A=50°,则∠B的度数为( )
| A. | 15° | B. | 20° | C. | 25° | D. | 30° |
16.下列图形中,不是中心对称图形的是( )
| A. | B. | C. | D. |
15.若a<b,则下列不等式成立的是( )
| A. | -a>-b | B. | -a+1>b+1 | C. | $\frac{1}{a}$>$\frac{1}{b}$ | D. | ac<bc |
14.某种衬衫的价格经过连续两次的降价后,由每件150元降到96元,则平均每次降价的百分率是( )
0 283962 283970 283976 283980 283986 283988 283992 283998 284000 284006 284012 284016 284018 284022 284028 284030 284036 284040 284042 284046 284048 284052 284054 284056 284057 284058 284060 284061 284062 284064 284066 284070 284072 284076 284078 284082 284088 284090 284096 284100 284102 284106 284112 284118 284120 284126 284130 284132 284138 284142 284148 284156 366461
| A. | 10% | B. | 15% | C. | 20% | D. | 30% |