求解个问题

P(Z<=1/2|X=0)=P(Y<=1/2|X=0)=P(Y<=1/2)
P(Z<=z)
=(1/3)[P(Z<=z|X=-1)+P(Z<=z|X=0)+P(Z<=z|X=1)]
=(1/3)[P(Y<=z+1|X=-1)+P(Y<=z|X=0)+P(Y<=z-1|X=1)]
=(1/3)[P(Y<=z+1)+P(Y<=z)+P(Y<=z-1)]
然后分z<=-1，-1<z<=0，0<z<=1，z>1四种情况算即可。