18.某体育用品商场为推销某一品牌运动服,先做了市场调查.得到数据如下表:
则P与x的函数关系式为p=-10x+1000,当卖出价格为60元/件时,则销售量为400件.
| 卖出价格x(元/件) | 50 | 51 | 52 | 53 | … |
| 销售量P(件) | 500 | 490 | 480 | 470 | … |
17.如图,是一组按照某种程度摆放成的图案,则图6中三角形的个数是( )
0 294093 294101 294107 294111 294117 294119 294123 294129 294131 294137 294143 294147 294149 294153 294159 294161 294167 294171 294173 294177 294179 294183 294185 294187 294188 294189 294191 294192 294193 294195 294197 294201 294203 294207 294209 294213 294219 294221 294227 294231 294233 294237 294243 294249 294251 294257 294261 294263 294269 294273 294279 294287 366461
| A. | 18 | B. | 19 | C. | 20 | D. | 21 |