1.8的平方根是( )
| A. | 2 | B. | 3 | C. | $2\sqrt{2}$ | D. | $±2\sqrt{2}$ |
19.
如图,矩形ABCD中,E是AD的中点,将△ABE沿BE折叠后得到△GBE,延长BG交CD于F点,若CF=2,FD=4,则BC的长为( )
| A. | 6$\sqrt{2}$ | B. | 2$\sqrt{3}$ | C. | 4$\sqrt{5}$ | D. | 4$\sqrt{6}$ |
18.若分式$\frac{x+1}{3x-2}$的值为零,则x等于( )
| A. | -l | B. | 1 | C. | $\frac{2}{3}$ | D. | 0 |
15.若a+b=5,ab=-24,则a2+b2的值等于( )
0 285395 285403 285409 285413 285419 285421 285425 285431 285433 285439 285445 285449 285451 285455 285461 285463 285469 285473 285475 285479 285481 285485 285487 285489 285490 285491 285493 285494 285495 285497 285499 285503 285505 285509 285511 285515 285521 285523 285529 285533 285535 285539 285545 285551 285553 285559 285563 285565 285571 285575 285581 285589 366461
| A. | 73 | B. | 49 | C. | 43 | D. | 23 |