12.
如图,等边△AOB和等边△ACD的一边都在x轴的正半轴,顶点B、D均在双曲线y=$\frac{4}{x}$(x>0)上,BC与AD相交于点P,则图中△BOP的面积为( )
| A. | 2$\sqrt{3}$ | B. | 3$\sqrt{3}$ | C. | 4$\sqrt{3}$ | D. | 4 |
11.若一元二次方程x2-3x-1=0的两根分别为x1,x2,则$\frac{1}{{x}_{1}}$+$\frac{1}{{x}_{2}}$的值为( )
| A. | 3 | B. | -3 | C. | $\frac{1}{3}$ | D. | -$\frac{1}{3}$ |
10.
如图,DE是△ABC的中位线,点F在DE上,且∠AFB=90°,若AB=5,BC=8,则EF的长为( )
| A. | 2.5 | B. | 1.5 | C. | 4 | D. | 5 |
9.用配方法解一元二次方程x2+6x-21=0时,配方正确的是( )
| A. | (x+3)2=30 | B. | (x+3)2=13 | C. | (x-3)2=30 | D. | (x-3)2=13 |
8.
如图,已知在?ABCD中,∠B=4∠A,则∠C=( )
| A. | 18° | B. | 36° | C. | 45° | D. | 72° |
4.平行四边形的周长为20cm,相邻两边的比为3:2,则此平行四边形较长的边长为( )
0 286590 286598 286604 286608 286614 286616 286620 286626 286628 286634 286640 286644 286646 286650 286656 286658 286664 286668 286670 286674 286676 286680 286682 286684 286685 286686 286688 286689 286690 286692 286694 286698 286700 286704 286706 286710 286716 286718 286724 286728 286730 286734 286740 286746 286748 286754 286758 286760 286766 286770 286776 286784 366461
| A. | 10cm | B. | 6cm | C. | 8cm | D. | 10cm |