19.下列运算正确的是( )
| A. | a•a-1=0 | B. | (a2)3=a6 | C. | -2×103=-20000 | D. | a6÷a2=a3 |
18.下列不等式组中解集为x<1的是( )
| A. | $\left\{\begin{array}{l}x<1\\ x<2\end{array}\right.$ | B. | $\left\{\begin{array}{l}x<1\\ x>2\end{array}\right.$ | C. | $\left\{\begin{array}{l}x>1\\ x>2\end{array}\right.$ | D. | $\left\{\begin{array}{l}x>1\\ x<2\end{array}\right.$ |
16.
如图,在Rt△ABC中,∠C=90°,∠B=30°,将Rt△ABC绕点A按顺时针方向旋转到△AB1C1的位置,使得点C、A、B1在同一条直线上,那么旋转角最小为( )
| A. | 115° | B. | 125° | C. | 120° | D. | 145° |
14.不等式2x+1>3的解集在数轴上表示正确的是( )
| A. | B. | C. | D. |
13.下列计算正确的是( )
| A. | a2+a2=a4 | B. | 2a-a=2 | C. | (a2)3=a5 | D. | (ab)2=a2b2 |
11.
如图所示,将△ABC绕点A按逆时针旋转50°后,得到△ADC′,则∠ABD的度数是( )
0 283144 283152 283158 283162 283168 283170 283174 283180 283182 283188 283194 283198 283200 283204 283210 283212 283218 283222 283224 283228 283230 283234 283236 283238 283239 283240 283242 283243 283244 283246 283248 283252 283254 283258 283260 283264 283270 283272 283278 283282 283284 283288 283294 283300 283302 283308 283312 283314 283320 283324 283330 283338 366461
| A. | 30° | B. | 45° | C. | 65° | D. | 75° |