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【简答题】
(1)设随机变量X的分布律为: 则E(X)=______;E(|X|)=______; =______. (填写小数) (2) 假设有十只同种电器元件,其中有两只不合格品.装配仪器时,从这批元件中只,如是不合格 品,则扔掉重新只;如仍是不合格品,则扔掉再取一只,则在取到合格品之前,已取出的不 合格品只数X的数学期望E[X]= 。 (填写a/b的分数形式)
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举一反三
【单选题】The cabin was built 50 years ago. I think it ’s(). Wehave to find another place to live.
A.
inhabitable
B.
uninhabitable
C.
hang
D.
handle
【判断题】A common American home during colonial times was the “log cabin”. Some houses were built of bricks, but wood was still the common building material.
A.
正确
B.
错误
【单选题】In early Colonial America settlers used makeshift shelters, the most primitive of which was the dugout, like a cave dug into the side of a hill, sometimes built up with sod and covered over with poles...
A.
made into a hillside
B.
more ambitious than a dugout
C.
without inside walls that might help to insulate
D.
possibly developed from those of the earlier inhabitants
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