12.若方程3x2-4x-4=0的两个实数根分别为x1,x2,则x1+x2=( )
| A. | -4 | B. | 3 | C. | $-\frac{4}{3}$ | D. | $\frac{4}{3}$ |
11.
如图,直线a∥b,∠1=55°,则∠2=( )
| A. | 35° | B. | 45° | C. | 55° | D. | 65° |
8.为了响应学校“书香校园”建设,阳光班的同学们积极捐书,其中宏志学习小组的同学捐书册数分别是:5,7,x,3,4,6.已知他们平均每人捐5本,则这组数据的众数、中位数和方差分别是( )
| A. | 5,5,$\frac{3}{2}$ | B. | 5,5,10 | C. | 6,5.5,$\frac{11}{6}$ | D. | 5,5,$\frac{5}{3}$ |
7.
如图,直线a∥b,直线c分别与a、b相交于A、B两点,AC⊥AB于点A,交直线b于点C.已知∠1=42°,则∠2的度数是( )
| A. | 38° | B. | 42° | C. | 48° | D. | 58° |
6.下列运算正确的是( )
| A. | a2•a3=a6 | B. | a5÷a2=a3 | C. | (-3a)3=-9a3 | D. | 2x2+3x2=5x4 |
5.-$\sqrt{2}$的相反数是( )
0 284052 284060 284066 284070 284076 284078 284082 284088 284090 284096 284102 284106 284108 284112 284118 284120 284126 284130 284132 284136 284138 284142 284144 284146 284147 284148 284150 284151 284152 284154 284156 284160 284162 284166 284168 284172 284178 284180 284186 284190 284192 284196 284202 284208 284210 284216 284220 284222 284228 284232 284238 284246 366461
| A. | -$\sqrt{2}$ | B. | $\frac{\sqrt{2}}{2}$ | C. | $\sqrt{2}$ | D. | -$\frac{\sqrt{2}}{2}$ |