设X1和X2分别表示掷两颗骰子各出现的点数，则有()
A.X1+X2 =2X2 B.E(X1) +E(X2) =2E(X1) C.Var(X1) + Var(X2) =4Var(X1) D.Var(X1X2) =4-Var(X1) E.E(X1) +E(X2) =3E(X1)正确答案BC
设X1和X2分别表示掷两颗骰子各出现的点数，则有()
A.X1+X2 =2X2 B.E(X1) +E(X2) =2E(X1) C.Var(X1) + Var(X2) =4Var(X1) D.Var(X1X2) =4-Var(X1) E.E(X1) +E(X2) =3E(X1)正确答案BC
