9.能说明命题“若0<α<90°,则2sinα≥1”是假命题,可以举的反例是( )
| A. | α=20° | B. | α=30° | C. | α=35° | D. | α=40° |
6.
如图,网格中小正方形的边长均为1,点A,B,C都在格点上,则∠ABC的正弦值是( )
| A. | $\frac{3}{5}$ | B. | $\frac{2\sqrt{5}}{5}$ | C. | $\frac{\sqrt{5}}{5}$ | D. | $\frac{4}{5}$ |
5.把-2xy-4x2y+2xy2提取公因式后,另一个因式是( )
| A. | -2-4x+2y | B. | -1-2x+y | C. | 1+2x-y | D. | 2x-y |
4.下列因式分解正确的是( )
0 295628 295636 295642 295646 295652 295654 295658 295664 295666 295672 295678 295682 295684 295688 295694 295696 295702 295706 295708 295712 295714 295718 295720 295722 295723 295724 295726 295727 295728 295730 295732 295736 295738 295742 295744 295748 295754 295756 295762 295766 295768 295772 295778 295784 295786 295792 295796 295798 295804 295808 295814 295822 366461
| A. | -2x2-2=-2(x+1)(x-1) | B. | x2-4x+4=(x-2)2 | C. | x2+9=(x+3)2 | D. | x2+3x+1=x(x+3)+1 |