设X,Y的方差存在,且E(XY)=EXEY,则() A.D(XY)=DXDY B.D(X+Y)=DX+DY C.X与Y独
1、设y=x+Inx,则dx/dy=() A、(x+1)/x B、(y+1)/y C、x/(x+1) D、y/(y+1)
y是x 的隐函数的导数,1)、xy-e^x+e^y=1,求y' .2)设y=sin(x+y),求dy/dx,d^2y/d
设(X,Y)为二维随机变量,证明:COV(X,Y)=E(XY)-EXEY
y=f(x)由方程xy+e^xy+y=e确定,求dy/dx和d^2y/dx^2
概率论的填空题,设X与Y是随机变量,且E(X)=E(Y)=1,D(X)=D(Y )=4,E(XY)=2,则D(2X-3Y
设X,Y为两个独立随机变量,且方差DX=3,DY=4,则D(X+Y)= ?
设DX=4,DY=2且X与Y独立,则D(3X-2Y)=?
设y=f(x) 由方程e^y=xy确定,则dy/dx=?
设 e^(x+y) - xy = 1,求 dy/dx \ x=0 y=0
设E(X)=1,E(Y)=2,D(X)=1,D(Y)=4,ρ(XY)=0.6,设Z=2X-Y+1,则其方差D(Z)=
设随机变量X与Y相互独立,方差D(X)与D(Y)存在,则有D(X+Y)=
设y=y(x) 由方程x^3+y^3=e^xy 确定,求 dy/dx!x=0的值