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(本题满分8分)设随机变量X的分布列为
(1)求常数α；X 123 4 P 0.2 0.3α 0.4 (2)求X的数学期望E(X)．
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- A.1
- B.1/2
- C.-1/2
- D.+∞
- A.<img src="//img1.yqda.net/question-name/a8/fe95735e7d1765569b75cb8370be0d.jpg" alt="" />
- B.<img src="//img1.yqda.net/question-name/f2/5b8df44f7276b2b5504a933a3d61d8.jpg" alt="" />
- C.当x→x0时, ?(x)- ?(x0)不是无穷小量
- D.当x→x0时, ?(x)- ?(X0)必为无穷小量
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- A.“5件都是正品”
- B.“5件都是次品”
- C.“至少有1件是次品”
- D.“至少有1件是正品”
- A.2cos x
- B.-2sin xcosx
- C.%
- D.2x
- A.-1/3
- B.-1/2
- C.1/3
- D.1/2
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- A.<img src="//img1.yqda.net/question-name/88/0bf063e9fd5b61ed4e1836fdce80bf.png" alt="" />
- B.<img src="//img1.yqda.net/question-name/b0/05f02bef09823d3b5469ee10844a27.png" alt="" />
- C.(0，1)
- D.<img src="//img1.yqda.net/question-name/cf/74f399c40dbb7d2d33b601f0017ba6.png" alt="" /><img src="//img1.yqda.net/question-name/eb/8d562688264ed123f4f30f30a46fa8.png" alt="" />
- A.<img src="//img1.yqda.net/question-name/01/173cbac4afd0944f4144bc1571c5c9.png" alt="" />
- B.<img src="//img1.yqda.net/question-name/9d/979477c1982d8e4966dbc89485533b.png" alt="" />
- C.<img src="//img1.yqda.net/question-name/f1/9f9cfc04ed43a89ebbbec35937987d.png" alt="" />
- D.<img src="//img1.yqda.net/question-name/97/2bce27f7e5549125a17ffdb1a133f6.png" alt="" />
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- A.<img src="//img1.yqda.net/question-name/e6/db7daba446fbd6ebf6a235e74d1c6d.jpg" height="12" width="50" />
- B.<img src="//img1.yqda.net/question-name/6c/a23670652895364fd73d58450c332f.jpg" height="26" width="41" />
- C.<img src="//img1.yqda.net/question-name/56/bccdb30db6ea39eb84251b9f644693.jpg" height="12" width="27" />
- D.<img src="//img1.yqda.net/question-name/21/143f64ea21ab62f9db73bd1be3308c.jpg" height="12" width="34" />
- A.<img src="//img1.yqda.net/question-name/74/497103c5bacb1aacbbad73db720159.jpg" height="12" width="53" />
- B.<img src="//img1.yqda.net/question-name/c7/4781ab586bd992274ac57245eb7aed.jpg" height="10" width="78" />
- C.<img src="//img1.yqda.net/question-name/ff/1ed4921a84ac782785b5999814310f.jpg" height="10" width="57" />
- D.<img src="//img1.yqda.net/question-name/e4/1cfd9cd804a824ccaa5a32ac219ef7.jpg" height="12" width="64" />
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- A.f(1，2)不是极大值
- B.f(1，2)不是极小值
- C.f(1，2)是极大值
- D.f(1，2)是极小值
