题干

某地政府落实党中央“精准扶贫”政策,解决一贫困山村的人畜用水困难,拟修建一个底面为正方形(由地形限制边长不超过10m)的无盖长方体蓄水池,设计蓄水量为800m3.已知底面造价为160元/m2,侧面造价为100元/m2

(I)将蓄水池总造价f(x)(单位:元)表示为底面边长x(单位:m)的函数;

(II)运用函数的单调性定义及相关知识,求蓄水池总造价f(x)的最小值.

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答案(点此获取答案解析)

解:(Ⅰ)设蓄水池高为h,则 h=800
x
2

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    What is the difference between developed and developing countries? The question is quite a difficult one. But we can compare them in two important aspects: people and economy.

    In developing countries there are high rates of both birth and death. Families decide to give birth to more than one child, because many developing countries do not have the systems necessary to guarantee(保证) the life of old people. Raising more children seems to be the only way to make sure that during their later years a person will be taken care of.

    The situation is completely different in fully-developed countries. Those countries have low levels of birth and mortality. Low mortality rate is mainly because of the good health care, but low birth rate is due to the fact that supporting a family with more children is expensive nowadays. Another reason is that more and more women decide to work outside, so there is usually no time and place for a large group of children in their lives.

    In developed countries, most industries have high levels of technological progress, while in developing countries most GDP comes from agriculture. It is mainly due to the fact that services and many branches of industry are in the stage of development. But they have the potential to develop quickly, because they have many things to improve.

    Of course, the difference between developed and developing countries is not that clear, because some countries might be in the middle of great changes. When a country is in that stage, some data can define the country as a developing one, but others may show that it is a developed one.