已知二维随机变量的概率密度,求边缘概率密度,
X的边缘密度函数f X(x)=积分(负无穷,正无穷)f(x,y)dy=积分(负无穷,正无穷)1/6 dy
=积分(0,2)1/6 dy
=1/3
Y的边缘密度函数f Y(y)=积分(负无穷,正无穷)f(x,y)dx
=积分(0,3)1/6 dx
=1/2
总范围是一个边长为3和2的长方形总面积=2*3=6 符合范围是一个等腰三角形面积为2*2/2=2
P(X+Y
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