设圆C1的方程为(x+2)2+(y-3m-2)2=4m2,直线l的方程为y=x+

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问题:

设圆C1的方程为(x+2)2+(y-3m-2)2=4m2,直线l的方程为y=x+m+2.

(1)若m=1,求圆C1上的点到直线l距离的最小值;

(2)求C1关于l对称的圆C2的方程;

(3)当m变化且m≠0时,求证:C2的圆心在一条定直线上,并求C2所表示的一系列圆的公切线方程.

考点:直线与圆的位置关系
题型:解答题

如果函数y=x2+ax-1在区间[0,3]上有最小值-2,求a的值.

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确定项目配套装置与工程的基本原则包括( )。

A.满足总图布置的要求

B.满足交通运输的要求

C.满足节能、节水的要求

D.经济合理

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阅读理解。

     The scene in the Hollywood movie The Day After Tomorrow, where global warming could soon turn the

global climate (气候) into a new ice age, may never occur, according to new research.

     The next ice age could be 15,000 years away, say European scientists who last month announced a

continuous record of 740,000 years of climate date (数据) obtained from the Antarctic ice.

     Scientists from 10 nations have now almost completely drilled through a 3,000-meter depth of ice high in

the Antarctic mainland. They figure out that the area where summer temperatures can fall to, has at least

900,000 years of snowfalls, kept as neatly as the growth rings of a tree. And the ice and air caught in each

layer (层) have begun to answer questions about the climates in the past.

     The results show that there have been eight ice ages in the past 740,000 years and eight warmer periods.

And by comparing the pattern of global conditions today with those of the past, the researchers reported in

Nature that the present warm period could last another 15,000 years.

     Research suggests that there is a very close connection between greenhouse gas levels and global average

temperatures. It also shows that carbon dioxide (二氧化碳) levels are the highest for at least 440,000 years.

     "If people say to you: the greenhouse effect is a good thing because we would go into an ice age

otherwise, our date say no, a new ice age is not hanging over our heads," said Eric Wolff from the British

Antarctic Survey." Now we have eight examples of how the climate goes in and out of ice ages … and you

can learn what the rules are that go into the climate models that tell us about the future."

     Scientists found that whenever temperatures rose in the frozen record, so did carbon dioxide level. " In

440,000 years we have never seen greenhouse gas get as thick as it is today," said Dr Wolff.

1. In drilling through the ice in Antarctica, scientists have found that _____.

A. the lowest temperature there is

B. the depth of ice is 3,000 meters

C. the ice has existed for 15,000 years

D. snowfalls are kept in certain patterns

2. The information of the global climate conditions in the past can be obtained through _____.

A. separating carbon dioxide from the air

B. examining the growth rings of trees

C. comparing temperatures in different areas

D. studying the ice and air caught in each layer

3. We can infer from Eric Wolff's words that _____.

A. there is something wrong with the data

B. greenhouse effect is always a bad thing

C. a new ice age will not come in the near future

D. greenhouse gas will get thick in the future

4. What would be the best title for the passage?

A. Research over the Antarctic area.

B. Warm period to last about 15,000 years.

C. Report on the eight ice ages in the past.

D. Hollywood movies and the global climate.

题型:解答题

下列哪项不是口腔流行病学的作用()

A.描述人群口腔健康与疾病的分布状态

B.为制定口腔相关的法律提供依据

C.研究疾病预防措施并评价其效果

D.监测口腔疾病流行趋势

E.研究口腔疾病的病因和影响流行的因素

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会计核算软件不包含报表处理功能。 ( )

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