设随机变量(X,Y)的联合密度函数为f(x,y)={21/4x^2y,x^2

问题描述：

设随机变量(X,Y)的联合密度函数为f(x,y)={21/4x^2y,x^2

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最佳答案：

fx(x)=∫x²~1 21/(4x²y) dy = (21/4x²)ln(y) |(y:x²~1) =(21/4x²)(-lnx²) fy|x(y|x)=f(x,y)/fx(x)=(1/y)/(-lnx²)=-1/(ylnx²)x=1/2时,密度函数=-1/(yln(1/4...