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问题 填空题

在测量某物理量的过程中，因仪器和观察的误差，使得n次测量分别得到a1，a2，…，an，共n个数据．我们规定所测量的“量佳近似值”a是这样一个量：与其他近似值比较，a与各数据的差的平方和最小．依此规定，从a1，a2，…，an推出的a=______．

答案

∵所测量的“量佳近似值”a是与其他近似值比较，

a与各数据的差的平方和最小．

根据均值不等式求平方和的最小值知这些数的底数要尽可能的接近，

∴a是所有数字的平均数，

∴a=

a1+a2+…+an
n
，

故答案为：

a1+a2+…+an
n

单项选择题

诊断急性坏死性龈炎时主要根据临床特征，但也有辅助诊断方法，其方法是（）。

A.活体组织检查

B.脱落细胞检查

C.坏死物及牙龈组织培养

D.坏死物涂片、革兰染色

E.细菌药物敏感试验
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改错题

It is good to see that today more people have realized the importance exercising and are playing sports regular. But the problem is that there are not enough sports facilities to meet the public growing demand. I love playing basketball and often play with my friends on weekends. Therefore, it is difficult to rent a basketball field and impossible to find a free one. It seems that all courts in the city were always full. Weather permitted, we can play in outdoors. But on rainy days or in winter we have to turn to indoor courts. There are not much in my city, and the charge is expensive. The government should build more public sports facilities, so easier accesses will encourage more people to participate in sports.
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