•Var(X+Y)= Var X + Var Y + 2 cov (X,Y)
•Var(X) = Cov (X, X)
•Var (X+a)= Var (X)
•Cov (X+a, Y+ b)= Cov(X,Y)
•Cov (aX, bY)=ab Cov(X,Y)
•Var(aX) =a2 Var (X)
•Cov( X+Y, Z)= cov(X,Z) + cov (Y,Z)
•Cov (X+Y, V+W)= cov(X,V) + cov (X, W) + cov (Y, W) +
cov(Y,W)
