D(X)=25,D(Y)=36,[img=58x17]17e0c5b1a8ccbe4.jpg[/img],则D(X+Y)=(),D(X-Y)=()
举一反三
- 设D(X)=25,D(Y)=36,[img=58x17]17e0bcfc3a8fb71.jpg[/img],则D(X+Y)=( ) A: 61 B: 85 C: 37 D: 57
- x+y=8()x-y=4()求x和y各等于几?A.()x=6()y=2()B.()x=5()y=3()C.()x=7()y=1()D.()x=3()y=5
- 若X和Y满足D(X+Y)=D(X-Y),则必有( ) A: X和Y独立 B: X和Y 不相关 C: D(Y)=0 D: D(X+Y) ·D(X-Y)=0
- 如果X,Y满足D(X-Y)=D(X+Y),则必有（ ） A: X,Y相互独立 B: Cov(X,Y)=0 C: D(Y)=0 D: D(X)D(Y)=0
- 设D(X)=4,D(Y)=9,03c1(X,Y)=0.5,则D(X-Y)=,D(X+Y)=