经济数学基础作(三)部分答案.doc

《经济数学基础》作业（三）部分答案 一、填空题 ⒈ ⒉ ⒊ ⒋ ⒌ ， 三、单项选择题 ⒈ A ⒉ B ⒊ C ⒋ B ⒌ C 三、解答题 ⒈解 ⑴∵，∴不能作为概率分布． ⑵∵，∴可以作为概率分布． ⒉解 ⒊解 已知，所以，由 得． ⒋解 ⑴ ∵ ∴不是密度函数． ⑵ ∵ 又∵ 可知在上单调增加，由此得 ∴是密度函数． ⒌解 由密度函数的性质知 得． ⒍解 ⑴设的密度函数为，则 ⑵密度函数的曲线为 ⑶ ⒎解 ⑴设的密度函数为，则 ⑵ ⒏解 由数学期望的定义得 由于被积函数是奇函数，所以 ⒐解 ⒑解 ⒒解 ⒓解 已知，所以 ⒔解 已知，所以 查表得，由此得出． ⒕解 已知，所以 由此可知数学成绩在分以上的学生约占该大学新生的． ⒖解 由分布列的性质得出 由此得出． ⒗解 ⑴ 由密度函数的性质知 得． ⑵ ⑶ ⒘解 ⑴ 由密度函数的性质知 得． ⑵ ⑶ ⒙解 由期望和方差的性质得到 ⒚解 已知，所以 practice activities implementation programme, and XX town party leadership party of mass line education practice activities rectification programme, and XX town carried out four wind aspects highlight problem special regulation implementation programme and XX town system construction plans,. One is to pay special attention to education. A party Lecture with 71 for all party members and cadres education, organizations watch anti-corruption warning education propaganda, promoting seven special and 9+1+X problems of rectification, Enhance the awareness of all the party members and cadres and the sense, honesty in politics and corruption of immunity. Second, well check the urge. Efforts to increase the annual implementation of the supervision to ensure completion of the various tasks. Third, conscientiously implement the Central, provincial, municipal and County requirements. All party members and cadres and workers to improve the style of work of the Organization, and strive to improve the leve