问题
选择题
已知某随机变量X的概率密度函数为P（x）=
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答案
由随机变量ξ的概率密度函数的意义知：
随机变量X落在区间（1，2）内的概率为
（e-x）dx=（-e-x） ∫ 21
=| 21
．e-1 e2
故选 D
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已知某随机变量X的概率密度函数为P（x）=
|
由随机变量ξ的概率密度函数的意义知：
随机变量X落在区间（1，2）内的概率为
（e-x）dx=（-e-x） ∫ 21
=| 21
．e-1 e2
故选 D
| 完形填空。 | ||||
| It was Molly's job to hand her father his paper lunch bag each morning before he went to work. One morning, besides his usual lunch bag, Molly 1 him a second paper bag. This one didn't look so good. It was 2 and was held together with tape (胶带). Her father kissed Molly and started off to work with the 3 bags. On his lunch break, while he was eating, he looked 4 the second old bag:two small dolls, three small stones and some coins. The busy father smiled, finished eating and 5 away the bags, dolls and stones. That 6 when they were having supper, Molly asked, "Where's my bag, Daddy?" "What bag?" "The one I gave 7 this morning." "I left it at the office. 8 ?" "I forgot to put this note in it," she said."Those are the 9 I really love. I thought you might like to 10 with them. You didn't lose the bag, did you,Daddy?" "Oh, no, "he said, lying (说谎). "I 11 forgot to bring it home. I'll bring it tomorrow." When Molly put her arms around her father's neck,he opened the 12 that read: "I love you, Daddy." Molly had given him her treasures (财富), 13 he had thrown them into the trash can (垃圾箱). So when he went back to the 14 , he went straight to the trash can and 15 all of Molly's things. He put the treasures inside the bag and carried it home. | ||||
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