题干

某地为促进淡水鱼养殖业的发展,将价格控制在适当范围内,决定对淡水鱼养殖提供政府补贴.设淡水鱼的市场价格为x元/千克,政府补贴为t元/千克.根据市场调查,当8≤x≤14时,淡水鱼的市场日供应量P千克与市场日需求量Q千克近似地满足关系:P=1000(x+t﹣8)( x≥8,t≥0),Q=50040-x-82(8≤x≤14).当P=Q时市场价格称为市场平衡价格.
(1)将市场平衡价格表示为政府补贴的函数,并求出函数的定义域;
(2)为使市场平衡价格不高于每千克10元,政府补贴至少为每千克多少元?
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答案(点此获取答案解析)

解:(1)依题设有
1000(x+t﹣8)=50040-x-82,
化简得5x2

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完形填空

    After my brother died in an accident, my mother was very sad. I was only 4 years old at the time, but I still understood the 1 in my mom's attitude toward safety.2, everything around us was potentially 3.

    I grew up with a lot of 4 and rules that were meant to 5 me. For example, I was not 6 to walk home from school by myself, even though everyone I knew already did. I couldn't 7 evening parties or go to summer camp,8 what if something happened to me?

    As I got older, the list of things to 9 got longer. I became a natural 10. I was concerned about things like getting cancer, losing my wallet, being caught in car accidents and earthquakes —11 big and small, real and 12.The funny part is that you'd never know it by looking at my life, because I'm constantly 13 myself to do the things that frighten or worry me. In fact, I've developed a 14 for myself: If it scares me, then I have to do it 15 once. I've done lots of things that would have 16 my mom: I've ridden a motorcycle, I've traveled alone, and I've performed stand-up comedy.

    Courage isn't a natural attribute (品质) of human beings. I believe that we have to practice being courageous. The more 17 I do things that scare me or that make me 18, the more I realize that I can do a lot more than I originally thought I could do.

    Even though I inherited (经遗传获得) my mother's cautious19, I've also come to believe that fear can be a good thing, if we 20 it. Believing that has made my world a less scary place.