9.下列方程组中,哪项的解是$\left\{\begin{array}{l}{x=-1}\\{y=-2}\end{array}\right.$( )
| A. | $\left\{\begin{array}{l}{x+y=1}\\{x-y=2}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=1}\\{x-2y=3}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{2x=y}\\{y+x=-3}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{\frac{x}{2}-\frac{y}{6}=1}\\{x+y=3}\end{array}\right.$ |
8.下面的多项式中,能因式分解的是( )
| A. | m2+(-n)2 | B. | m2-m+1 | C. | m2-n | D. | m2-2m+1 |
3.下列命题是假命题的是( )
| A. | 邻补角一定互补 | |
| B. | 不重合的两条直线只有两种位置关系:相交和平行 | |
| C. | 对顶角相等 | |
| D. | 垂线段最短 |
2.下列实数中,是无理数的为( )
0 282510 282518 282524 282528 282534 282536 282540 282546 282548 282554 282560 282564 282566 282570 282576 282578 282584 282588 282590 282594 282596 282600 282602 282604 282605 282606 282608 282609 282610 282612 282614 282618 282620 282624 282626 282630 282636 282638 282644 282648 282650 282654 282660 282666 282668 282674 282678 282680 282686 282690 282696 282704 366461
| A. | 3.1415926 | B. | $\frac{2}{7}$ | C. | $\sqrt{6}$ | D. | $\root{3}{27}$ |