证明 左边 = ∑(-1)”aA…(b,+c,a 12j% = ∑(-1)a…ba hjz-In + ∑(-1-a4…c%a i2j =右边证明 左边 1 2 1 1 2 1 2 1 1 2 1 2 1 1 2 ( ) 1 ( ) 1 ( ) 1 ( 1) ( ) ( 1) ( 1) n i i n n n i n n n i n n j j j j j j nj j j j j j j j j nj j j j j j j j j nj j j j a b c a a b a a c a    = − + = − + − =    右边