在概率统计中有这样一道题：设随机变量X的密度函数为f(x)={3/8x^2,0

E(X)=∫【0,2】xf(x)dx=3/8*∫【0,2】x^3dx=3/8*1/4*x^4|【0,2】=3/2
E(X^2)=∫【0,2】x^2f(x)dx=3/8*∫【0,2】x^4dx=3/8*1/5*x^5|【0,2】=12/5
E(1/X^2)=∫【0,2】1/x^2*f(x)dx=3/8*∫【0,2】dx=3/8*x|【0,2】=3/4
解毕