15.下列计算正确的是( )
| A. | 2a+3b=5ab | B. | a3•a2=a6 | C. | (a-b)2=a2-b2 | D. | (a2)4=a8 |
12.计算(-2xy2)3的结果是( )
| A. | -2x3y6 | B. | -6x3y6 | C. | 8x3y6 | D. | -8x3y6 |
11.计算a2b•a的结果是( )
| A. | a3b | B. | 2a2b | C. | a2b2 | D. | a2b |
10.
如图,AB是⊙O的直径,CD是⊙O的弦,连接AD、DB、BC,若∠ABD=55°,则∠BCD的度数为( )
0 283098 283106 283112 283116 283122 283124 283128 283134 283136 283142 283148 283152 283154 283158 283164 283166 283172 283176 283178 283182 283184 283188 283190 283192 283193 283194 283196 283197 283198 283200 283202 283206 283208 283212 283214 283218 283224 283226 283232 283236 283238 283242 283248 283254 283256 283262 283266 283268 283274 283278 283284 283292 366461
| A. | 65° | B. | 55° | C. | 45° | D. | 35° |