方程组x-2y=0x2+y2=20的解是______.

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问题:

方程组
x-2y=0
x2+y2=20
的解是______.
考点:三元(及三元以上)一次方程(组)的解法
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数轴上到原点的距离为2的点所表示的数是______.

题型:填空题

阅读理解。

     These two letters appeared in a newspaper. Both writers have their own ideas on zoos.

                                                      Zoos Do a Good Job

     It is good to keep animals in zoos. I know a lot of people think it is wrong to keep animals in zoos.

However, I believe that zoos have many good points.

     Firstly, zoos are places for people to see many different kinds of animals from all the world. Without

zoos, most people would never see a real bear or tiger.

     Secondly, zoos. look after the animals very well. The animals are given food and cleaned regularly

(定期). In the wild, it is not always possible for an animal to find food, so sometimes it goes hungry.

But animals kept in zoos never go hungry.

     Thirdly, zoos protect the animals they look after. They offer them safe places to live in. In the wild,

some kinds of animals are in danger of becoming extinct (灭绝). But zoos give these animals a chance

tolive. Without zoos, there would be fewer kinds of animals in the world.

                                                                                                                   Maria Smith

                                                        Zoos Are Unnatural

     In Maria's letter, she says that zoos are good for animals. I'm afraid that zoos are not good for

animals, they are only good for people.

     It is unnatural and unfair to keep wild animals in cages. Most animals are kept in cages that

are too small for them. In the wild, these animals would travel freely. In zoos. they can't do this. This is

why the bears and tigers always look so sad.

     Most cages are not very clean, either. It is true that zoos give the animals food regularly, but this is

not natural. Wild animals are used to l00 — king for them own food. We should treat animals in the

same way that we treat other people-with respect. Would anyone be happy if you don't let him go

outside his home? Would Maria like to have lots of people standing .outside her flat l00 -king at

her? No, she wouldn't. And animals don't like it, either.

                                                                                                                      Philip Black

根据短文内容,判断正(T) 误 (F) 。

( )1. Maria and Philip have quite different ideas on keeping animals in zoos.

(     )2. In Maria's opinion (观点), a real bear or tiger can only be seen in zoos.

(     )3. Maria thinks that animals live better in zoos than in the wild.

(     )4. According to Philip, if cages are big and clean enough, tigers and bears will look happy.

(     )5. In the two letters, they are discussing how to make animals in zoos happy.

题型:填空题

以下所列举出的物理量中属于矢量的有(  )

A.时间

B.质量

C.速度

D.速率

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射吸式焊炬的优点是可以使用低压乙炔,乙炔的压力达到()MPA甚到更低都有可维持正常操作。

A.0.003

B.0.03

C.0.3

D.0.13

题型:填空题

混凝能除去水中大部分的(),沉淀、过虑能彻底除去水中的()。

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