某学校有2500名学生，其中高一1000人，高二900人，高三600人，为了了解学生的身体健康状况，采用分层抽样的方法，若从本校学生中抽取100人，从高一和高三抽取样本数分别为a，b，且直线ax+by+8=0与以A（1，﹣1）为圆心的圆交于B，C两点，且∠BAC=120°，则圆C的方程为（   ）

看图列式计算。

    A rich man loved his little boy very much. He wanted 1  him happy all the time. So he gave him everything that he could buy with   2 . But the little boy was still  3  .Where he went, he always wore a frown(皱眉). And he always wished for something he did not have. The rich man didn't know   4  to make his son happy.
    One day, a magician(魔术师) came and said to him, “I can make your son happy and  5  his frowns into smiles, but you must pay me a great price   6 telling him the secret.”
   “All right,” said the man, “No matter what you ask for, I  7  you.”The magician took the boy into a secret room. He wrote something on a piece of paper, and then gave it to the boy. There were some words on the paper, “Do one  8  thing for someone every day.” The boy followed the  9   and became one of the happiest boys.
    I think only those who are always thinking about   10  can be truly happy.

化简求值：（$\sqrt{x}$-$\frac{x}{x+\sqrt{x}}$）÷$\frac{x-\sqrt{x}}{\sqrt{x}}$，其中x=2+$\sqrt{2}$．

塑化剂是工业上被广泛使用的高分子材料助剂，在塑料加工中添加这种物质，可以使其柔韧性增强，容易加工．塑化剂可合法用于工业生产，但禁止作为食品添加剂．截止2011年6月8日，台湾被检测出含塑化剂食品已达961种，据媒体报道，2012年岁末，我国大陆多种著名品牌白酒也陷入了塑化剂风波．常见塑化剂为邻苯二甲酸酯类物质，某有机物J（C₁₉H₂₀O₄）是一种塑料工业中常用的塑化剂，可用下列合成路线合成．

已知：Ⅰ．

+RCl→ +NaCl；

Ⅱ．控制反应条件，使物质A中的支链Y不与NaOH溶液发生反应；

Ⅲ．F与浓溴水混合不产生白色沉淀．

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