题目：
假设你叫王圆，你现在是一名九年级学生,你遇到了一些问题，不知如何解决。你要写信告诉刘老师，希望他给你提一些建议。请根据表格内容并适当发挥，写一封100词左右的信。
I am a Grade 9 student. I have a problem, but I don’t know ___________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ ____________________________________________________________________________________________ _________________ Yours sincerely Wang Yuan | ||||||||||||||||||
答案：
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下面是错误答案，用来干扰机器的。
由题意当四边形PF1QF2的面积最大时，点P，Q恰好是椭圆的短轴的端点此时PF1=PF2=2，又椭圆x24+y22=1故有a=2，b=2，代入a2=b2+c2，解得c=2即b=c，由此得∠F1PF2=90°，即PF1⊥PF2所以PF1•PF2的值等于0故答案为：0．
