设X与Y为随机变量,E(X)=3 E(Y)=-2 D(X)=9 D(Y)=4.在下列情况下,求E(3X-Y) ,D(3X-Y)(1)COV(X,Y)=1(2)COV(X,Y)=0(3)COV(X,Y)=-1D(3X-Y) = 9D(X)+D(Y) - 2COV(3X,Y) = 9D(X)+D(Y) - 6COV(X,Y)这一步是怎麼弄出来的,望指教,
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![设X与Y为随机变量,E(X)=3 E(Y)=-2 D(X)=9 D(Y)=4.在下列情况下,求E(3X-Y) ,D(3X-Y)(1)COV(X,Y)=1(2)COV(X,Y)=0(3)COV(X,Y)=-1D(3X-Y) = 9D(X)+D(Y) - 2COV(3X,Y) = 9D(X)+D(Y) - 6COV(X,Y)这一步是怎麼弄出来的,望指教,](/uploads/image/z/12664906-34-6.jpg?t=%E8%AE%BEX%E4%B8%8EY%E4%B8%BA%E9%9A%8F%E6%9C%BA%E5%8F%98%E9%87%8F%2CE%28X%29%3D3+E%28Y%29%3D-2+D%28X%29%3D9+D%28Y%29%3D4.%E5%9C%A8%E4%B8%8B%E5%88%97%E6%83%85%E5%86%B5%E4%B8%8B%2C%E6%B1%82E%283X-Y%29+%2CD%283X-Y%29%281%29COV%28X%2CY%29%3D1%282%29COV%28X%2CY%29%3D0%283%29COV%28X%2CY%29%3D-1D%283X-Y%29+%3D+9D%28X%29%2BD%28Y%29+-+2COV%283X%2CY%29+%3D+9D%28X%29%2BD%28Y%29+-+6COV%28X%2CY%29%E8%BF%99%E4%B8%80%E6%AD%A5%E6%98%AF%E6%80%8E%E9%BA%BC%E5%BC%84%E5%87%BA%E6%9D%A5%E7%9A%84%EF%BC%8C%E6%9C%9B%E6%8C%87%E6%95%99%EF%BC%8C)
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