17.若分式$\frac{x-1}{x+1}$的值为零,则x的值是( )
| A. | 0 | B. | 1 | C. | -1 | D. | -2 |
15.下列各组中的四条线段是比例线段的是( )
| A. | 1cm,2cm,20cm,40cm | B. | 1cm,2cm,3cm,4cm | ||
| C. | 3cm,4cm,6cm,9cm | D. | 5cm,10cm,15cm,20cm |
14.一个多边形的每个外角是60°,则该多边形边数是( )
| A. | 5 | B. | 6 | C. | 7 | D. | 8 |
13.
已知S△ABC=4cm2,点E为BC中点,点D为BE中点,则S△ABD=( )cm2.
| A. | 2 | B. | 3 | C. | 1 | D. | 1.5 |
12.已知b<0.则a,a-b,a+b中最大的是( )
| A. | a | B. | a+b | C. | a-b | D. | 以上都不对 |
11.下列二次根式中,不能与$\sqrt{6}$合并的是( )
0 288440 288448 288454 288458 288464 288466 288470 288476 288478 288484 288490 288494 288496 288500 288506 288508 288514 288518 288520 288524 288526 288530 288532 288534 288535 288536 288538 288539 288540 288542 288544 288548 288550 288554 288556 288560 288566 288568 288574 288578 288580 288584 288590 288596 288598 288604 288608 288610 288616 288620 288626 288634 366461
| A. | $\sqrt{\frac{2}{3}}$ | B. | $\sqrt{24}$ | C. | $\sqrt{1.5}$ | D. | $\sqrt{1.2}$ |