19.若函数y=(m-1)x2+3x+1是二次函数,则有( )
| A. | m≠0 | B. | m≠1 | C. | x≠0 | D. | x≠1 |
12.
有12米长的木条,要做成一个如图的窗框,如果假设窗框横档的长度为x米,那么窗框的面积是(木条的宽度忽略不计)( )
| A. | x(6-$\frac{3}{2}$x)米2 | B. | x(12-x)米2 | C. | x(6-3x)米2 | D. | x(6-x)米2 |
11.下列计算正确的是( )
| A. | 45.5°=45°30′ | B. | 3a+b=3ab | C. | -$\frac{1}{2}$>-$\frac{1}{3}$ | D. | a3+a2=a5 |
10.全国“双创周”活动在深圳湾创业广场启幕,未来三年,国家将投入8500亿元用于大众创业万众创新,将8500亿元用科学记数法表示为( )
0 293839 293847 293853 293857 293863 293865 293869 293875 293877 293883 293889 293893 293895 293899 293905 293907 293913 293917 293919 293923 293925 293929 293931 293933 293934 293935 293937 293938 293939 293941 293943 293947 293949 293953 293955 293959 293965 293967 293973 293977 293979 293983 293989 293995 293997 294003 294007 294009 294015 294019 294025 294033 366461
| A. | 8.5×103亿元 | B. | 0.85×104亿元 | C. | 8.5×104亿元 | D. | 85×102亿元 |