阅读理解
I live in a nice new building in Beijing. It is very tall. It has eighteen floors. There are about eighty families in the building. That is to say (也就是说), about two hundred and forty people live in the building.
My home is on the twelfth floor. We have two bedrooms and a living room. They are big and clean. There are a lot of big trees and beautiful flowers around our building. I like looking out of the window in my room. I can see cars and buses running in the street. I can see people walking in the street, too. They look so small! I can also see a lot of tall buildings. How beautiful Beijing is! I am happy to live in this nice, new and tall building.
满足
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成等差数列，则
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