p(x=x1)=2/3,p(x=x2)=1/3 x1
问题描述：
p(x=x1)=2/3,p(x=x2)=1/3 x1
答
EX= x1*(2/3) + x2*(1/3) = 4/3 ==> 2x1+x2=4DX=E(X^2) - (EX)^2 = x1^2*(2/3)+x2^2*(1/3) - (4/3)^2 = 2/9 ==> 2x1^2+x2^2=6所以,解得：x1=1,x2=2,或者 x1=5/3,x2=2/3因为 x1