12.
如图,平面直角坐标系中,矩形ABCD的边AB:BC=3:2,点A(3,0),B(0,6)分别在x轴,y轴上,反比例函数y=$\frac{k}{x}$的图象经过点D,则k值为( )
| A. | -14 | B. | 14 | C. | 7 | D. | -7 |
9.
如图,在平面直角坐标系中,四边形ABCD是菱形,∠ABC=60°,且点A的坐标为(4,0),若E是AD的中点,则点E的坐标为( )
| A. | (-2,2$\sqrt{3}$) | B. | (2,-4$\sqrt{3}$) | C. | (-2,4$\sqrt{3}$) | D. | (2,-2$\sqrt{3}$) |
7.下列各式中计算正确的是( )
| A. | (x+y)2=x2+y2 | B. | 3x2=6x2 | C. | a2+a2=a4 | D. | (x2)3=x6 |
6.已知(m+n)2=1,(m-n)2=9,则mn=( )
| A. | -2 | B. | 2 | C. | -3 | D. | 3 |
4.下列说法正确的是( )
0 296797 296805 296811 296815 296821 296823 296827 296833 296835 296841 296847 296851 296853 296857 296863 296865 296871 296875 296877 296881 296883 296887 296889 296891 296892 296893 296895 296896 296897 296899 296901 296905 296907 296911 296913 296917 296923 296925 296931 296935 296937 296941 296947 296953 296955 296961 296965 296967 296973 296977 296983 296991 366461
| A. | 0的算术平方根是0 | B. | 9是3的算术平方根 | ||
| C. | ±3是9的算术平方根 | D. | -3是9的算术平方根 |