A . I=J
B . I=2J
C . I=3J
D . I=4J
[单选题]已知D(X)=1,D(Y)=16,ρXY=0.5,则D(X+Y)=( )A.18B.19C.21D.17
设平面区域D由 x=0 ,y=0 +y=dfrac (1)(2) ,x+y=1 围成,记 _(1)=iint (ln )^3(x+y)dxdy --|||-_(
17、已知 D(X)=9 ,D(Y)=36 ,(rho )_(x)y=0.4 ,则 (dfrac (1)(3)X+dfrac (1)(6)Y)=D(X+Y)=-
已知D(X)=4,D(Y)=1,rho xy=0.6,求D(X+Y),D(3X-2Y)已知D(X)=4,D(Y)=1,,求D(X+Y),D(3X-2Y)
设_(1)= int ln (x+y)dxdy-|||-D,_(1)= int ln (x+y)dxdy-|||-D,其中_(1)= int ln (x+y)d
[单选题]已知D(X)=2,D(Y)=3,则Cov(X+Y,X-Y)等于().A . 1B . -1C . 5D . 6
设X与Y是两个随机变量,已知D(X) =1,D(Y) =2,cov(X,Y) =0.3,则D(2 X+Y) = ____.(填空题,3.0分)设X与Y是两个随机
D(Y)=8 ,X,Y相互独立则 D(X+Y)= __
设随机变量X~N(0,1),Y~N(0,1),则X+Y()A. 服从正态分布N(0,1)B. 服从正态分布N(0,2)C. $$ 服从正态分布N(0, \sqr
D(X) =1,D(Y) =2,X与Y相互独立,Z=2 X+Y,则D(Z) = ( )A 1 B 2 C 4 D 6D(X)=1,D(Y)=2,X与Y相互独立,