B'r(a)B2 得方程组如下： nx? 2 (x,- 62 B i= n i=l ∑(x,-x. ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 2 2 0 1 2 0 1 0 1 0 2 1 2 1 2 1 1                                 + = + = =          = = = =     + + − + − +  = + + − + + − t e dt e dt t x e dx v X E X x e dx t t x t x x 令 得方程组如下：          = − = = − =         = + =    = = = 2 1 2 2 2 1 2 2 1 2 2 1 1          ~ x ( x x ) nx ˆ ~ x ( x x ) nx ˆ x n ( ) x n i i n i i n i i