15.已知关于x、y的方程组$\left\{\begin{array}{l}{x+y=-3m}\\{x-y=4+m}\end{array}\right.$满足x>0且y<0,则m的取值范围是( )
| A. | m>1 | B. | m<2 | C. | -1<m<2 | D. | 1<m<2 |
14.实数n、m是连续整数,如果n<$\sqrt{17}$<m,那么m+n的值为( )
| A. | 9 | B. | 10 | C. | 11 | D. | 12 |
13.下列关于整式的运算结果正确的是( )
| A. | 2x•(-xy)2=-2x3y | B. | (-x2)3÷(-x3)2=1 | ||
| C. | ($\frac{3}{4}$a3-$\frac{1}{2}$b)•2ab=$\frac{3}{2}$a4b-ab2 | D. | (3m-1)2=9m2-1 |
10.
如图,∠ACB=90°,∠ABC=30°,AD平分∠BAC,DE⊥AB,DE=2.5cm,AC=4cm,则△ABC的周长为( )
0 297678 297686 297692 297696 297702 297704 297708 297714 297716 297722 297728 297732 297734 297738 297744 297746 297752 297756 297758 297762 297764 297768 297770 297772 297773 297774 297776 297777 297778 297780 297782 297786 297788 297792 297794 297798 297804 297806 297812 297816 297818 297822 297828 297834 297836 297842 297846 297848 297854 297858 297864 297872 366461
| A. | 19.5cm | B. | 20cm | C. | 20.5cm | D. | 19cm |