8.
已知,∠AOB=30°,点M1,M2,M3…在射线OB上,点N1,N2,N3…在射线0A上,△M1N1M2,△M2N2M3,△M3N3M4…均为等边三角形.若OM1=1,则△M9N9M10长为( )
| A. | 32 | B. | 64 | C. | 128 | D. | 256 |
5.
如图,在Rt△ABC中,∠B=90°,分别以A、C为圆心,大于AC长的一半为半径画弧,两弧相交于点M、N,连接MN,与AC、BC分别相交于点D、E,连接AE,当AB=3,AC=5时,△ABE周长为( )
| A. | 7 | B. | 8 | C. | 9 | D. | 10 |
3.方程(x-5)(x+8)=x-5的解是( )
| A. | x=-7 | B. | x=5或x=-8 | C. | x=5或x=-7 | D. | x=5 |
20.已知一个正方形的面积是15,那么它的边长是( )
0 286720 286728 286734 286738 286744 286746 286750 286756 286758 286764 286770 286774 286776 286780 286786 286788 286794 286798 286800 286804 286806 286810 286812 286814 286815 286816 286818 286819 286820 286822 286824 286828 286830 286834 286836 286840 286846 286848 286854 286858 286860 286864 286870 286876 286878 286884 286888 286890 286896 286900 286906 286914 366461
| A. | 15 | B. | $\sqrt{15}$ | C. | $\frac{1}{15}$ | D. | 以上皆不对 |