EW=E(2X)+E(Y)=2EX+EY=1
EV=EX-E(3Y)=-3
DW=D(2X)+D(Y)+2cov(2X,Y)=4DX+DY+4*cov(X,Y)=37
DV=DX+D(3Y)-2cov(X,3Y)=DX+9DY-6cov(X,Y)=67
cov(W,V)=cov(2X+Y,X-3Y)=2DX-6cov(x,Y)+cov(X,Y)-3DY=-34--->
(W,V)的联合分布~N(1,-3,37,67,-34/(2479)^(1/2))
E(WV)用积分算,太繁杂略去
N(3,1),P(|X-3|>2)<=DX/2^2=1/4