20.
正方形A1B1C1O,A2B2C2C1,A3B3C3C2,…按如图的方式放置.点A1,A2,A3,…和点C1,C2,C3,…分别在直线y=x+1和x轴上,则点Bn的坐标是( )
| A. | (2n-1,2n-1) | B. | (2n-1,2n-1) | C. | (2n,2n-1) | D. | (2n-1,2n) |
18.计算($\frac{2}{3}$)2015×1.52015的结果是( )
| A. | $\frac{2}{3}$ | B. | -$\frac{2}{3}$ | C. | 1 | D. | -$\frac{3}{2}$ |
15.在△ABC中,∠C=60°,∠B=70°,则∠A的度数是( )
| A. | 70° | B. | 55° | C. | 50° | D. | 40° |
13.下列各式由左边到右边的变形,是因式分解的是( )
①(a+3)(a-3)=a2-9 ②m2-4=(m+2)(m-2)
③a2-b2+1=(a+b)(a-b)+1 ④2mR+2mr=2m(R+r)
①(a+3)(a-3)=a2-9 ②m2-4=(m+2)(m-2)
③a2-b2+1=(a+b)(a-b)+1 ④2mR+2mr=2m(R+r)
| A. | ①② | B. | ②③ | C. | ③④ | D. | ②④ |
12.下列交通标志中,轴对称图形的个数是( )

0 284235 284243 284249 284253 284259 284261 284265 284271 284273 284279 284285 284289 284291 284295 284301 284303 284309 284313 284315 284319 284321 284325 284327 284329 284330 284331 284333 284334 284335 284337 284339 284343 284345 284349 284351 284355 284361 284363 284369 284373 284375 284379 284385 284391 284393 284399 284403 284405 284411 284415 284421 284429 366461
| A. | 4个 | B. | 3个 | C. | 2个 | D. | 1个 |