定理63得出 无法显示该图片 E(x)=B(x)=1Bx)=1∑Ex=1∑ p=p Dx)=D∑x)=1D∑x)=1zDx)=m2=▪ 定理6.3得出 1 1 1 1 1 1 1 ( ) ( ) ( ) n n n n i i i i i i i E X E X E X EX n n n n   = = = = = = = =     2 2 2 2 2 1 1 1 1 1 1 ( ) ( ) ( ) ( ) n n n iii i i i n D X D X D X D X n n n n n   = = = = = = = =   