求解概率题，在线等，急！！！

Question

如题所述

Answer 1

P(X=-1) = P(U≦-1) = 1/4
P(X=1) = P(U >-1) = 3/4
P(Y=-1) = P(U ≦1) = 3/4
P(Y=1) = P(U >1) = 1/4

P(Y=-1|X=-1) = P(Y=-1|U ≦-1) = 1
P(Y=1|X=-1) = P(Y=1|U ≦-1) = 0

Z=X+Y

P(Z=-2)=P(X=-1,Y=-1)=P(Y=-1|X=-1)P(X=-1)=(1)(1/4)=1/4

P(Z=0)=P(X=1,Y=-1)+P(X=-1,Y=1)
=P(Y=-1|X=1)P(X=1)+P(Y=1,X=-1)P(X=-1)
=P(U≦1|U>-1)(3/4)+(1/4)
=(1/2)(3/4)+(1/4)=5/8

P(Z=2)=P(X=1,Y=1)
=P(Y=1|X=1)P(X=1)
=P(U>1|U>-1)(3/4)
=(1/3)(3/4)=1/4

关于Z的计算, 有误. 请你自己重算下. 你能搞定的.