9.已知函数y=$\sqrt{2x-4}$在实数范围内有意义,则自变量x的取值范围是( )
| A. | x≥2 | B. | x>2 | C. | x≤2 | D. | x<2 |
5.下列多项式乘法中,可用平方差公式计算的是( )
| A. | (2a+b)(2a-3b) | B. | (x-2y)(x+2y) | C. | (x+1)(1+x) | D. | (-x-y)(x+y) |
3.
如图,将一副三角板如图放置,∠COD=20°,则∠AOB的度数为( )
0 296777 296785 296791 296795 296801 296803 296807 296813 296815 296821 296827 296831 296833 296837 296843 296845 296851 296855 296857 296861 296863 296867 296869 296871 296872 296873 296875 296876 296877 296879 296881 296885 296887 296891 296893 296897 296903 296905 296911 296915 296917 296921 296927 296933 296935 296941 296945 296947 296953 296957 296963 296971 366461
| A. | 140° | B. | 150° | C. | 160° | D. | 170° |