19.若分式方程$\frac{x}{x-1}$-1=$\frac{m}{(x-1)(x+2)}$无解,则m=( )
| A. | 0和3 | B. | 1 | C. | 1和-2 | D. | 3 |
18.运用平方差公式计算(x+2y-1)(x-2y+1),下列变形正确的是( )
| A. | [x-(2y+1)]2 | B. | [x+(2y-1)][x-(2y-1)] | C. | [(x+2y)-1][(x-2y)+1] | D. | [x+(2y+1)]2 |
17.若代数式x2-10x+k是一个完全平方式,则k=( )
0 279610 279618 279624 279628 279634 279636 279640 279646 279648 279654 279660 279664 279666 279670 279676 279678 279684 279688 279690 279694 279696 279700 279702 279704 279705 279706 279708 279709 279710 279712 279714 279718 279720 279724 279726 279730 279736 279738 279744 279748 279750 279754 279760 279766 279768 279774 279778 279780 279786 279790 279796 279804 366461
| A. | 25 | B. | 25或-25 | C. | 10 | D. | 5或-5 |