14.下列计算正确的是( )
| A. | (x-2)2=x2-4 | B. | (m+n)2=m2+n2 | C. | (x+2)(x-2)=x2-4 | D. | (m-n)2=m2-2mn-n2 |
13.
如图,直线a∥b,直线c与直线a,b都相交,若∠1=55°,则∠2等于( )
| A. | 55° | B. | 45° | C. | 35° | D. | 25° |
12.人体内有一种细胞的直径约为0.00000156米,将数0.00000156用科学记数法为( )
| A. | 1.56×10-5 | B. | 1.56×10-6 | C. | 1.56×10-7 | D. | 15.6×10-6 |
8.
如图,在Rt△ABC中,∠ACB=90°,AC=2$\sqrt{3}$,BC=6,动点P,Q分别在边AB,BC上,则CP+PQ的最小值为( )
| A. | 3$\sqrt{3}$ | B. | 3+$\frac{3\sqrt{3}}{2}$ | C. | 2$\sqrt{3}$ | D. | 2+$\sqrt{3}$ |
6.地球与月球之间的平均距离是38.4万千米,数据“38.4万”用科学记数法表示为( )
0 294358 294366 294372 294376 294382 294384 294388 294394 294396 294402 294408 294412 294414 294418 294424 294426 294432 294436 294438 294442 294444 294448 294450 294452 294453 294454 294456 294457 294458 294460 294462 294466 294468 294472 294474 294478 294484 294486 294492 294496 294498 294502 294508 294514 294516 294522 294526 294528 294534 294538 294544 294552 366461
| A. | 38.4×104 | B. | 3.84×105 | C. | 3.84×106 | D. | 3.84×104 |