设随机变量(X,Y)的概率密度为f(x,y)=Be^-(x+y),0
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设随机变量(X,Y)的概率密度为f(x,y)=Be^-(x+y),0
由归一性有:∫(从0积到1)∫(从0积到+∞) B*e^[-(x+y)] dydx = B*∫(从0积到1) e^(-x) dx * ∫(从0积到+∞) e^(-y) dy = B*[1 - e^(-1)]*1 = B*[1 - e^(-1)] = 1
所以B = e/(e - 1)
x的边缘密度函数fx(x) = ∫(从0积到+∞) e/(e-1) * e^[-(x+y)] dy = [e^(1-x)]/(e-1)
y的边缘密度函数fy(y) = ∫(从0积到1) e/(e-1) * e^[-(x+y)] dx = [e^(2-y)]/[(e-1)^2]
所以B = e/(e - 1)
x的边缘密度函数fx(x) = ∫(从0积到+∞) e/(e-1) * e^[-(x+y)] dy = [e^(1-x)]/(e-1)
y的边缘密度函数fy(y) = ∫(从0积到1) e/(e-1) * e^[-(x+y)] dx = [e^(2-y)]/[(e-1)^2]
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