问题 填空题

已知AB为抛物线y2=2px(p>0)的焦点弦,若|AB|=m,则AB中点的横坐标为_____________.

答案

抛物线y2=2px的焦点弦长|AB|=|AF|+|BF|=(x1+)+(x2+)=x1+x2+p=m,

=.

∴AB中点横坐标为.

材料题

阅读下列材料:

        材料一:乾隆帝致英国国王乔治三世的信中说:“天朝物产丰盈,无所不有,原不藉外夷货物以通有无。”

       材料二:清嘉庆帝上谕说:“天朝富有四海,岂需尔小国些微货物哉?”

(1)这些材料说明我国当时实行的是一种什么政策?为什么实行这种政策?

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                             

(2)这种政策的含义是什么?

                                                                                                                                                             

(3)联系当前现实谈谈你从中得到什么启示?

                                                                                                                                                             

(4)你认为在对待外来事物方面今天我们应如何去做?

                                                                                                                                                              

                                                                                                                                                              

单项选择题