18.空气的密度是0.001293g/cm3,0.001293用科学记数法表示为( )
| A. | 1.293×103 | B. | 1.293×10-3 | C. | 1.293×10-4 | D. | 12.93×10-4 |
17.下列图形中,是轴对称图形的是( )
| A. | B. | C. | D. |
16.
如图,能表示点B到直线AC的距离的线段是( )
| A. | BC | B. | BD | C. | BA | D. | AD |
14.
如图,正六边形ABCDEF内接于圆O,半径为4,则这个正六边形的边心距OM和弧BC的长分别为( )
| A. | 2$\sqrt{3}$、$\frac{4π}{3}$ | B. | 2$\sqrt{3}$、π | C. | $\sqrt{3}$、$\frac{2π}{3}$ | D. | 2、$\frac{π}{3}$ |
13.在百度上搜索“一带一路”,显示找到相关结果约52 900 000个,将数字52 900 000用科学记数法表示为( )
| A. | 52.9×107 | B. | 0.529×108 | C. | 5.29×108 | D. | 5.29×107 |
11.
如图,四边形ABCD中,对角线AC、BD相交于点O,下列条件不能判定这个四边形是平行四边形的是( )
| A. | AB∥DC,AD∥BC | B. | AB∥DC,AD=BC | C. | AO=CO,BO=DO | D. | AB=DC,AD=BC |
10.下列变形中,正确的是( )
0 297224 297232 297238 297242 297248 297250 297254 297260 297262 297268 297274 297278 297280 297284 297290 297292 297298 297302 297304 297308 297310 297314 297316 297318 297319 297320 297322 297323 297324 297326 297328 297332 297334 297338 297340 297344 297350 297352 297358 297362 297364 297368 297374 297380 297382 297388 297392 297394 297400 297404 297410 297418 366461
| A. | -$\frac{1}{a}$=$\frac{-1}{a}$ | B. | $\frac{1}{a}$+$\frac{1}{b}$=$\frac{1}{a+b}$ | C. | $\frac{2{b}^{2}}{{a}^{2}}$=$\frac{2b}{a}$ | D. | $\frac{a+ab}{b+ab}$=$\frac{a}{b}$ |