春秋时期管仲认为：任何商品都是“重则至，轻则去”。所以，国家要采取两大策略：一是“敛轻散重”，购进人们所轻者，抛售人们所重者。二是“以重射轻”，用高价收购市场上跌幅较大的商品，以改进商品价低滞销的状态，使物价稳定下来。管仲提出的策略蕴涵的经济生活道理有                               
①人们的喜好决定商品的供求             ②商品的价格与供求相互制约
③价格变动有利于提高劳动生产率        ④稳定物价是政府调控经济的重要目标

某学校研究性学习小组搜集了如图两幅图来探究影响气候的部分因素．请你参与进来完成下列问题探究．

根据短文理解，选择正确答案填空。 

    Jim is a junior high school student. He gets up 16:30 every morning. His home is near his school. He 2home after breakfast. He goes to school on foot. This is good for his 3. He has four lessons in the morning. He has lunch at home. After lunch he goes to school again. In the afternoon, Jim has lessons . He likes English and PE lessons. He has PE lessons on Tuesday and Friday. He is good at4football and basketball. He is also good at the high jump. His PE teacher likes5 very much. He often plays football with his classmates after school.

从直接原因来看，现阶段我国之所以实行按劳分配，是因为（   ）

勾股定理神秘而美妙，它的证法多样，其巧妙各有不同，其中的“面积法”给了小聪以灵感，他惊喜的发现，当两个全等的直角三角形如图1或图2摆放时，都可以用“面积法”来证明，下面是小聪利用图1证明勾股定理的过程：

将两个全等的直角三角形按图1所示摆放，其中∠DAB=90°，求证：a²+b²=c²

证明：连结DB，过点D作BC边上的高DF，则DF=EC=b﹣a

∵S_{四边形ADCB}=S_△ACD+S_△ABC= $\frac{1}{2}$ b²+ $\frac{1}{2}$ ab．

又∵S_{四边形ADCB}=S_△ADB+S_△DCB= $\frac{1}{2}$ c²+ $\frac{1}{2}$ a（b﹣a）

∴ $\frac{1}{2}$ b²+ $\frac{1}{2}$ ab= $\frac{1}{2}$ c²+ $\frac{1}{2}$ a（b﹣a）

∴a²+b²=c²

请参照上述证法，利用图2完成下面的证明．

将两个全等的直角三角形按图2所示摆放，其中∠DAB=90°．求证：a²+b²=c²．