随机变量(X,Y)概率密度为f(x,y)=e^(-y)(0

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随机变量(X,Y)概率密度为f(x,y)=e^(-y)(0
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随机变量(X,Y)概率密度为f(x,y)=e^(-y)(0
随机变量(X,Y)概率密度为f(x,y)=e^(-y)(0

随机变量(X,Y)概率密度为f(x,y)=e^(-y)(0
1.f(X,Y)关于X的边缘概率密度fX(x)=f(x,y)对y积分,下限x,上限无穷,结果fX(x)=e^(-x)
2.f(X,Y)关于Y的边缘概率密度fY(y)=f(x,y)对x积分,下限0,上限y,结果fY(y)=ye^(-y)
3.f(x,y)=e^(-y)不等于fX(x)*fY(y),故X和Y不独立
4.概率密度函数f(x,y)在直线x=0,y=x,y=-x 1所围的三角形区域的二重积分,结果是1 e^(-1)-2e^(-1/2)