3.下列计算正确的是( )
| A. | x+x2=x3 | B. | 2x+3x=5x2 | C. | (x2)3=x5 | D. | x5÷x3=x2 |
2.实数$\sqrt{2}-1$的相反数是( )
| A. | -1-$\sqrt{2}$ | B. | $\sqrt{2}+1$ | C. | 1-$\sqrt{2}$ | D. | $\sqrt{2}-1$ |
19.下列变形是因式分解的是( )
| A. | xy(x+y)=x 2 y+xy 2 | B. | x 2+2x+1=x(x+1)+1 | ||
| C. | (a-b)(m-n)=(b-a)(n-m) | D. | ab-a-b+1=(a-1)(b-1) |
18.下列各组数中,互为相反数的是( )
| A. | 2-3与 23 | B. | (-2)-2与2-2 | C. | 33 与(-$\frac{1}{3}$)3 | D. | (-3)-3与($\frac{1}{3}$)3 |
17.已知x+y=3,xy=$\frac{1}{2}$,则多项式3x2+3y2的值为( )
0 285397 285405 285411 285415 285421 285423 285427 285433 285435 285441 285447 285451 285453 285457 285463 285465 285471 285475 285477 285481 285483 285487 285489 285491 285492 285493 285495 285496 285497 285499 285501 285505 285507 285511 285513 285517 285523 285525 285531 285535 285537 285541 285547 285553 285555 285561 285565 285567 285573 285577 285583 285591 366461
| A. | 24 | B. | 20 | C. | 15 | D. | 13 |