A.X与Y相互独立
B.X与Y不相关
C.D(Y)=0
D.D(X)·D(Y)=0
[问答题]D(X)=4,D(Y)=9,ρXY=0.5,则D(X-Y)=----------,D(X+Y)=------------.
[问答题]D(X)=4,D(Y)=9,ρXY=0.5,则D(X-Y)=-------------,D(X+Y)=-------------.
[单选题]已知D(X)=2,D(Y)=3,则Cov(X+Y,X-Y)等于().A . 1B . -1C . 5D . 6
[单选题]将2(x+y)-3(x-y)-4(x+y)+5(x-y)-3(x-y)合并同类项得()。A.-3x-yB.-2(x+y)C.-x+yD.-2(x+y)
[单选题]将2(x+y)-3(x-y)-4(x+y)+5(x-y)-3(x-y)合并同类项得()。A.-3x-yB.-2(x+y)C.-x+yD.-2(x+y)
[单选题]已知D:x+y≤1,D1:x≥0,y≥0,x+y≤1,,则()。A . I=JB . I=2JC . I=3JD . I=4J
[单选题]设(x-y)(x+2+y)-15=0,则x+y的值是()。A.-5或3B.-3或5C.3D.5
[单选题]已知D(X)=1,D(Y)=16,ρXY=0.5,则D(X+Y)=( )A.18B.19C.21D.17
[问答题]已知D(X)=25,D(Y)=36,X与Y的相关系数ρXY=0.4,则D(X+Y)=().
[单选题]已知D(X)=4,D(Y)=9,Cov(X+Y)=2,则D(3X-2Y)等于().A . 96B . 72C . 48D . 36