17.设全集U={1,2,3,4,5,6},A={2,4,6}则CUA=( )
A. | {1,3,5,6} | B. | {1,3,5} | C. | {2,3,4} | D. | {1,2,3,5} |
13.经过圆x2-4x+y2=0的圆心C,且与直线x+y=0垂直的直线方程是( )
A. | x+y+2=0 | B. | x+y-2=0 | C. | x-y+2=0 | D. | x-y-2=0 |
12.已知$\overrightarrow{a},\overrightarrow{b}$是单位向量,它们的夹角为1200,则$\overrightarrow{a}•(\overrightarrow{a}-\overrightarrow{4b})$的值为( )
0 252250 252258 252264 252268 252274 252276 252280 252286 252288 252294 252300 252304 252306 252310 252316 252318 252324 252328 252330 252334 252336 252340 252342 252344 252345 252346 252348 252349 252350 252352 252354 252358 252360 252364 252366 252370 252376 252378 252384 252388 252390 252394 252400 252406 252408 252414 252418 252420 252426 252430 252436 252444 266669
A. | 3 | B. | -1 | C. | $1+2\sqrt{3}$ | D. | $1-2\sqrt{3}$ |