8.若(m-1)2与$\sqrt{n+2}$互为相反数,则P(-m,-n)在第( )象限.
| A. | 一 | B. | 二 | C. | 三 | D. | 四 |
7.下列方程组中是二元一次方程组的是( )
| A. | $\left\{\begin{array}{l}{x-y=3}\\{xy=1}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{2x+y=5}\\{x=3y-2}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{{x}^{2}-y=1}\\{y=2x}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{\frac{1}{y}-x=2}\\{x+y=0}\end{array}\right.$ |
5.已知方程组$\left\{\begin{array}{l}ax-by=4\\ ax+by=2\end{array}\right.$的解为$\left\{\begin{array}{l}x=1\\ y=2\end{array}\right.$,则3a-2b的值为( )
0 283624 283632 283638 283642 283648 283650 283654 283660 283662 283668 283674 283678 283680 283684 283690 283692 283698 283702 283704 283708 283710 283714 283716 283718 283719 283720 283722 283723 283724 283726 283728 283732 283734 283738 283740 283744 283750 283752 283758 283762 283764 283768 283774 283780 283782 283788 283792 283794 283800 283804 283810 283818 366461
| A. | 8 | B. | 10 | C. | -10 | D. | -8 |