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【简答题】
设随机变量X的分布律为 X -2 0 2 P 0.4 0.3 0.3 求D(3X 2 +5)，D(-2X 2 -8)．
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举一反三
【单选题】As more women in the United States are working now, more are finding it necessary to make business trips alone. Since this is still new for many, some tips are certainly in order. If you are married, ...
A.
Working women who have no time for cooking.
B.
Husbands and children of working women.
C.
Working women traveling by themselves.
D.
Restaurant managers who serve working women.
【简答题】随着天然大理石石材加工工艺的不断改进，厚度较小的板材也开始应用于装饰工程，常见的厚度有（ ）等，亦称为薄板。
【简答题】世界上开凿最早,里程最长的人工大运河是
【单选题】As more women in the United States are working now, more are finding it necessary to make business trips alone. Since this is still new for many, some tips are certainly in order. If you are married, ...
A.
Working women who have no time for cooking.
B.
Husbands and children of working women.
C.
Working women traveling by themselves.
D.
Restaurant managers who serve working women.
【多选题】常见的板形表示方法：（）、此外还有矢量表示法、残余应力表示法、断面形状的多项式表示法和厚度相对变化量差表示法。为了保证板形良好，必须遵守均匀延伸或板凸度一定的原则，使其横断面各点延伸率或压缩率基本相等。
A.
板凸度
B.
楔形
C.
相对长度表示法
D.
波形表示法
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