1.9的算术平方根是( )
| A. | 3 | B. | -3 | C. | ±3 | D. | ±9 |
18.
如图,AB是半圆的直径,点D是$\widehat{AC}$的中点,∠ABC=50°,则∠DAB等于( )
| A. | 65° | B. | 60° | C. | 55° | D. | 50° |
17.
如图,在平面直角坐标系中有△ABC,以点O为位似中心,相似比为2,将△ABC放大,则它的对应顶点的坐标为( )
| A. | (2,$\frac{3}{2}$),($\frac{3}{2},\frac{1}{2}$),($\frac{1}{2},1$) | B. | (8,6)(6,2)(2,4) | ||
| C. | (8,6)(6,2)(2,4)或(-8,-6)(-6,-2)(-2,-4) | D. | (8,-6)(6,-2)(2,-4)或(-8,6)(-6,2)(-2,4) |
15.
如图,已知△OAB与△OA′B′是相似比为 1:2 的位似图形,点O为位似中心,若△OAB内一点P(x,y)与△OA′B′内一点P′是一对对应点,则点P′的坐标为( )
| A. | (-x,-y) | B. | (-2x,-2y) | C. | (-2x,2y) | D. | (2x,-2y) |
14.设A=$\sqrt{24}$+3,A在两个相邻整数之间,则这两个整数是( )
| A. | 5和6 | B. | 6和7 | C. | 7和8 | D. | 8和9 |
13.下列图形中,轴对称图形的个数( )

0 283985 283993 283999 284003 284009 284011 284015 284021 284023 284029 284035 284039 284041 284045 284051 284053 284059 284063 284065 284069 284071 284075 284077 284079 284080 284081 284083 284084 284085 284087 284089 284093 284095 284099 284101 284105 284111 284113 284119 284123 284125 284129 284135 284141 284143 284149 284153 284155 284161 284165 284171 284179 366461
| A. | 1 个 | B. | 2 个 | C. | 3 个 | D. | 4 个 |