5.已知圆O的方程为x2+y2=4,P为圆O上的一个动点,若OP的垂直平分线总是被平面区域x2+y2≥a2覆盖,则实数a的取值范围是( )
| A. | [-1,1] | B. | [0,1] | C. | [-2,2] | D. | [0,2] |
2.设f(x)是连续的偶函数,且当x>0时是单调函数,则满足f(x)=f($\frac{x+1}{2x+4}$)的所有x之和为( )
0 234171 234179 234185 234189 234195 234197 234201 234207 234209 234215 234221 234225 234227 234231 234237 234239 234245 234249 234251 234255 234257 234261 234263 234265 234266 234267 234269 234270 234271 234273 234275 234279 234281 234285 234287 234291 234297 234299 234305 234309 234311 234315 234321 234327 234329 234335 234339 234341 234347 234351 234357 234365 266669
| A. | -$\frac{3}{2}$ | B. | -$\frac{5}{2}$ | C. | -4 | D. | 4 |