9.若m>n,则下列不等式中一定成立的是( )
| A. | m+2<n+3 | B. | 2m<3n | C. | a-m<a-n | D. | ma2>na2 |
6.
菱形ABCD中,如图,AE⊥BC于E,AF⊥CD于F,若BE=EC,则∠EAF=( )
| A. | 75° | B. | 60° | C. | 50° | D. | 45° |
5.将 3a2m-6amn+3a分解因式,下面是四位同学分解的结果:
①3am(a-2n+1)②3a(am+2mn-1)③3a(am-2mn) ④3a(am-2mn+1)
其中,正确的是( )
①3am(a-2n+1)②3a(am+2mn-1)③3a(am-2mn) ④3a(am-2mn+1)
其中,正确的是( )
| A. | ① | B. | ② | C. | ③ | D. | ④ |
4.已知$\left\{\begin{array}{l}{x=1}\\{y=2}\end{array}\right.$是二元一次方程2x+ay=4的一个解,则a的值为( )
0 297707 297715 297721 297725 297731 297733 297737 297743 297745 297751 297757 297761 297763 297767 297773 297775 297781 297785 297787 297791 297793 297797 297799 297801 297802 297803 297805 297806 297807 297809 297811 297815 297817 297821 297823 297827 297833 297835 297841 297845 297847 297851 297857 297863 297865 297871 297875 297877 297883 297887 297893 297901 366461
| A. | 2 | B. | -2 | C. | 1 | D. | -1 |