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There are many holidays and festivals. Dads have Father's Day. Children have Children's Day. Is there a special day for old people?

Double Ninth Festival is a special day for old people in China. It started long ago. The festival is on lunar September 9th. This year it is on October 13th. On this day, people show love for their grandparents.

People do many different kinds of things on this day. They enjoy flowers, eat special cakes and drink wine(酒).

      It's very interesting. The best way to celebrate it is climbing hills or mountains. People think climbing will bring them good luck and help old people live long lives. Double Ninth Festival is also a good time for a family get-together. And young people give their presents and best wishes to the old.

一元二次方程(x-9)²=0的解是（　）

在平面直角坐标系xOy中，O为坐标原点，C、D两点的坐标为C（﹣1，0），D（1，0），曲线E上的动点P满足$\left|PC\right|+\left|PD\right|=2\sqrt{3}$．又曲线E上的点A、B满足OA⊥OB．求曲线E的方程.