(1)a+0.2=0.3,故a=0.1;0.3+0.4+0.1+b=1,故b=0.2. (2)P(X=-1)=0.3,P(X=0)=0.4,P(X=2)=0.3;
P(Y=1)=0.5,P(Y=3)=0.5. (3)E(X)=-1*0.3+0*0.4+2*0.3=0.3 D(X)=E(X^2)-(E(X))^2
=1*0.3+0*0.4+4*0.3-0.3^2=1.41 (4)X,Y不独立,因为p(X=0,Y=3)=0.1,而p(X=0)p(Y=3)=0.4*0.5=0.2
不相等,故不独立。(5)P(Z=-1)=0.3 P(Z=0)=0.4 P(Z=1)=0.1 P(Z=2)=0.2
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