题干

已知圆C:x2+(y﹣3)2=4,点A(0,﹣3),M是圆上任意一点,线段AM的中垂线l和直线CM相交于点Q,则点Q的轨迹方程为____  .

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答案(点此获取答案解析)

y2-
x
2
8
=1

同类题1

阅读理解

    Birthdays often involve surprises. But this year's surprise on the birthday of the great British playwright William Shakespeare is surely one of the most dramatic.

    On April 22, one day before his 441st birthday anniversary, experts discovered that one of the most recognizable portraits of William Shakespeare is a fake. This means that we no longer have a good idea of what Shakespeare looked like. “It's very possible that many pictures of Shakespeare might be unreliable because many of them are copies of this one,” said an expert from Britain's National Portrait Gallery.

    The discovery comes after four months of testing using X-rays, ultraviolet light, microphotography and paint samples. The experts from the gallery say the image —commonly known as the “Flower portrait”— was actually painted in the 1800s, about two centuries after Shakespeare's death. The art experts who work at the gallery say they also used modern chemistry technology to check the paint on the picture. These checks found traces of paint dating from about 1814. Shakespeare died in 1616, and the date that appears on the portrait is 1609.

    “We now think the portrait dates back to around 1818 to 1840. This was when there was a renewed interest in Shakespeare's plays,” Tarnya Cooper, the gallery's curator (馆长), told the Associated President.

    The fake picture has often been used as a cover for collections of his plays. It is called the Flower portrait because one of its owners, Desmond Flower, gave it to the Royal Shakespeare Company.

    “There have always been questions about the painting,” said David Howells, curator for the Royal Shakespeare Company. “Now we know the truth, we can put the image in its proper place in the history of Shakespearean portraiture.”

    Two other images of Shakespeare, are also being studied as part of the investigation and the results will come out later this month.________

同类题5

随着对生态和环境保护认识的日益深入,人们意识到在发展经济的同时,必须注意对生态和环境的保护,实现社会效益、经济效益、生态效益的并举和优化。

作物

农药施用量

/千克·公顷-1

农药流失率

/%

作物收入

/元·公顷-1

作物投资费

/元

1

6

15

1000

1500 n

2

2.5

20

700

600 n

注: n 中的n表示作物所种的公顷数。

现有一个较大的生态系统,其中包括1000公顷(1公顷=10000米2)的农田、一个1.0×1052的湖泊以及一种必须加以保护的食鱼鹰等。又有2种可供选择种植的经济作用(作物1和作物2),一年只能种植一季,有关这2种作物种植所涉及的一些参数见上表。由表可知,不同作物的经费投入、收入、施药量及流失率不同。

湖水最初未受污染,种植作物后,会因农药的流失,有一定量的农药由流经农田的水流带入湖泊(假定流入湖泊中的农药不会流失),而湖泊中水的体积常年稳定在2.0×1053。湖水中的农药会沿着食物链:浮游藻类→食藻鱼类→食鱼鹰,在生物体内逐步积累,越到食物链的后端,体内农药的质量分数越大。假定该种食鱼鹰体内最大可承受的农药质量分数为2.69×10-4,由此换算出湖水中农药的质量分数最大不能超过4.05×10-6

(注:①因源水质量巨大,在计算过程中可将湖水质量视作溶液质量;② 1000 32)请你运用所学的知识回答下列问题: